feat: Add Infrahub Jinja2 transforms for MLAG configuration (#22) (#26)

## Summary

Closes #22. Implements Infrahub Jinja2 transforms for MLAG configuration, generating Arista-native YANG-compatible JSON payloads from Infrahub intent data.

| File | Description |
|------|-------------|
| `infrahub/transforms/queries/mlag_intent.gql` | GraphQL query — fetches `InfraMlagPeerConfig` by `$device_name`, including MLAG domain attributes, peer/iBGP VLANs, local interface SVI, and peer-link LAG |
| `infrahub/transforms/templates/mlag_yang.j2` | Jinja2 template — renders a JSON object targeting `/arista-mlag-augments:mlag/config`; returns `[]` for devices with no MLAG (spines) |
| `infrahub/transforms/tests/mlag_yang/test.yml` | Test spec: smoke check + unit render tests for `leaf1` and `spine1` |
| `infrahub/transforms/tests/mlag_yang/leaf1/` | Mock input + expected output for leaf1 (full MLAG config, domain `leafs-1-2`) |
| `infrahub/transforms/tests/mlag_yang/spine1/` | Mock input (empty edges) + expected output `[]` for spine1 |
| `.infrahub.yml` | Registers `mlag_intent` query and `mlag_yang_transform` jinja2 transform |

## Output shape (leaf1)

```json
{
  "mlag": {
    "config": {
      "domain-id": "leafs-1-2",
      "peer-link": "Port-Channel999",
      "local-interface": "Vlan4090",
      "peer-address": "10.0.199.255",
      "shutdown": false
    },
    "dual_primary_detection": {
      "enabled": true,
      "delay": 10,
      "action": "errdisable",
      "heartbeat_peer_ip": "172.16.0.50",
      "heartbeat_vrf": "mgmt"
    },
    "virtual_mac": "c001.cafe.babe",
    "peer_vlan_id": 4090,
    "ibgp_vlan_id": 4091,
    "local_interface_ip": "10.0.199.254/31"
  }
}
```

## Validation

```bash
infrahubctl render mlag_yang_transform device_name=leaf1   # → MLAG config JSON
infrahubctl render mlag_yang_transform device_name=spine1  # → []
```

## Design notes

- Follows identical conventions to existing transforms (#20 VLAN/interface/VXLAN, #21 VRF/L3VNI)
- All optional relationship accesses wrapped in `is defined and is not none` guards
- Spine/non-MLAG devices return `[]` (empty array) — consistent with the "no data → empty collection" pattern used in vxlan_yang for devices without VTEP

.infrahub.yml

@@ -26,6 +26,8 @@ queries:
     file_path: infrahub/transforms/queries/vxlan_intent.gql
   - name: vrf_intent
     file_path: infrahub/transforms/queries/vrf_intent.gql
+  - name: mlag_intent
+    file_path: infrahub/transforms/queries/mlag_intent.gql
 
 jinja2_transforms:
   - name: vlan_yang_transform
@@ -44,3 +46,7 @@ jinja2_transforms:
     description: "Generate VRF/L3VNI configuration payload from Infrahub intent"
     query: vrf_intent
     template_path: infrahub/transforms/templates/vrf_yang.j2
+  - name: mlag_yang_transform
+    description: "Generate MLAG configuration payload from Infrahub intent"
+    query: mlag_intent
+    template_path: infrahub/transforms/templates/mlag_yang.j2

infrahub/transforms/queries/mlag_intent.gql

@@ -0,0 +1,53 @@
+query MlagIntent($device_name: String!) {
+  InfraMlagPeerConfig(device__name__value: $device_name) {
+    edges {
+      node {
+        local_interface_ip { value }
+        peer_address { value }
+        heartbeat_peer_ip { value }
+        device {
+          node {
+            name { value }
+          }
+        }
+        mlag_domain {
+          node {
+            domain_id { value }
+            virtual_mac { value }
+            heartbeat_vrf { value }
+            dual_primary_detection { value }
+            dual_primary_delay { value }
+            dual_primary_action { value }
+            devices {
+              edges {
+                node {
+                  name { value }
+                }
+              }
+            }
+            peer_vlan {
+              node {
+                vlan_id { value }
+              }
+            }
+            ibgp_vlan {
+              node {
+                vlan_id { value }
+              }
+            }
+          }
+        }
+        local_interface {
+          node {
+            name { value }
+          }
+        }
+        peer_link {
+          node {
+            name { value }
+          }
+        }
+      }
+    }
+  }
+}

infrahub/transforms/templates/mlag_yang.j2

@@ -0,0 +1,90 @@
+{#
+  mlag_yang.j2 — Produce a JSON object with the MLAG configuration payload
+  for a single device, targeting Arista-native YANG paths.
+
+  Input: GraphQL response from mlag_intent query.
+  Returns an empty array [] if the device has no MLAG peer config (e.g. spines).
+
+  Output structure:
+  {
+    "mlag": {
+      "config": { ... },          # /arista-mlag-augments:mlag/config
+      "dual_primary_detection": { ... },
+      "virtual_mac": "...",
+      "peer_vlan_id": ...,
+      "ibgp_vlan_id": ...,
+      "local_interface_ip": "..."
+    }
+  }
+#}
+{%- set peer_configs = data.InfraMlagPeerConfig.edges -%}
+
+{%- if peer_configs | length == 0 -%}
+[]
+{%- else -%}
+  {%- set cfg = peer_configs[0].node -%}
+
+  {#— Resolve local interface name —#}
+  {%- set local_iface_name = none -%}
+  {%- if cfg.local_interface is defined and cfg.local_interface is not none and cfg.local_interface.node is not none -%}
+    {%- set local_iface_name = cfg.local_interface.node.name.value -%}
+  {%- endif -%}
+
+  {#— Resolve peer-link name —#}
+  {%- set peer_link_name = none -%}
+  {%- if cfg.peer_link is defined and cfg.peer_link is not none and cfg.peer_link.node is not none -%}
+    {%- set peer_link_name = cfg.peer_link.node.name.value -%}
+  {%- endif -%}
+
+  {#— Resolve MLAG domain attributes —#}
+  {%- set domain_id = none -%}
+  {%- set virtual_mac = none -%}
+  {%- set heartbeat_vrf = none -%}
+  {%- set dual_primary_detection = false -%}
+  {%- set dual_primary_delay = none -%}
+  {%- set dual_primary_action = none -%}
+  {%- set peer_vlan_id = none -%}
+  {%- set ibgp_vlan_id = none -%}
+
+  {%- if cfg.mlag_domain is defined and cfg.mlag_domain is not none and cfg.mlag_domain.node is not none -%}
+    {%- set domain = cfg.mlag_domain.node -%}
+    {%- set domain_id = domain.domain_id.value -%}
+    {%- set virtual_mac = domain.virtual_mac.value | default(none) -%}
+    {%- set heartbeat_vrf = domain.heartbeat_vrf.value | default("mgmt") -%}
+    {%- set dual_primary_detection = domain.dual_primary_detection.value | default(false) -%}
+    {%- set dual_primary_delay = domain.dual_primary_delay.value | default(none) -%}
+    {%- set dual_primary_action = domain.dual_primary_action.value | default(none) -%}
+
+    {%- if domain.peer_vlan is defined and domain.peer_vlan is not none and domain.peer_vlan.node is not none -%}
+      {%- set peer_vlan_id = domain.peer_vlan.node.vlan_id.value -%}
+    {%- endif -%}
+
+    {%- if domain.ibgp_vlan is defined and domain.ibgp_vlan is not none and domain.ibgp_vlan.node is not none -%}
+      {%- set ibgp_vlan_id = domain.ibgp_vlan.node.vlan_id.value -%}
+    {%- endif -%}
+  {%- endif -%}
+
+  {%- set result = {
+    "mlag": {
+      "config": {
+        "domain-id": domain_id,
+        "peer-link": peer_link_name,
+        "local-interface": local_iface_name,
+        "peer-address": cfg.peer_address.value,
+        "shutdown": false
+      },
+      "dual_primary_detection": {
+        "enabled": dual_primary_detection,
+        "delay": dual_primary_delay,
+        "action": dual_primary_action,
+        "heartbeat_peer_ip": cfg.heartbeat_peer_ip.value,
+        "heartbeat_vrf": heartbeat_vrf
+      },
+      "virtual_mac": virtual_mac,
+      "peer_vlan_id": peer_vlan_id,
+      "ibgp_vlan_id": ibgp_vlan_id,
+      "local_interface_ip": cfg.local_interface_ip.value
+    }
+  } -%}
+{{ result | tojson(indent=2) }}
+{%- endif -%}

infrahub/transforms/tests/mlag_yang/leaf1/input.json

@@ -0,0 +1,96 @@
+{
+  "data": {
+    "InfraMlagPeerConfig": {
+      "edges": [
+        {
+          "node": {
+            "local_interface_ip": {
+              "value": "10.0.199.254/31"
+            },
+            "peer_address": {
+              "value": "10.0.199.255"
+            },
+            "heartbeat_peer_ip": {
+              "value": "172.16.0.50"
+            },
+            "device": {
+              "node": {
+                "name": {
+                  "value": "leaf1"
+                }
+              }
+            },
+            "mlag_domain": {
+              "node": {
+                "domain_id": {
+                  "value": "leafs-1-2"
+                },
+                "virtual_mac": {
+                  "value": "c001.cafe.babe"
+                },
+                "heartbeat_vrf": {
+                  "value": "mgmt"
+                },
+                "dual_primary_detection": {
+                  "value": true
+                },
+                "dual_primary_delay": {
+                  "value": 10
+                },
+                "dual_primary_action": {
+                  "value": "errdisable"
+                },
+                "devices": {
+                  "edges": [
+                    {
+                      "node": {
+                        "name": {
+                          "value": "leaf1"
+                        }
+                      }
+                    },
+                    {
+                      "node": {
+                        "name": {
+                          "value": "leaf2"
+                        }
+                      }
+                    }
+                  ]
+                },
+                "peer_vlan": {
+                  "node": {
+                    "vlan_id": {
+                      "value": 4090
+                    }
+                  }
+                },
+                "ibgp_vlan": {
+                  "node": {
+                    "vlan_id": {
+                      "value": 4091
+                    }
+                  }
+                }
+              }
+            },
+            "local_interface": {
+              "node": {
+                "name": {
+                  "value": "Vlan4090"
+                }
+              }
+            },
+            "peer_link": {
+              "node": {
+                "name": {
+                  "value": "Port-Channel999"
+                }
+              }
+            }
+          }
+        }
+      ]
+    }
+  }
+}

infrahub/transforms/tests/mlag_yang/leaf1/output.json

@@ -0,0 +1,22 @@
+{
+  "mlag": {
+    "config": {
+      "domain-id": "leafs-1-2",
+      "peer-link": "Port-Channel999",
+      "local-interface": "Vlan4090",
+      "peer-address": "10.0.199.255",
+      "shutdown": false
+    },
+    "dual_primary_detection": {
+      "enabled": true,
+      "delay": 10,
+      "action": "errdisable",
+      "heartbeat_peer_ip": "172.16.0.50",
+      "heartbeat_vrf": "mgmt"
+    },
+    "virtual_mac": "c001.cafe.babe",
+    "peer_vlan_id": 4090,
+    "ibgp_vlan_id": 4091,
+    "local_interface_ip": "10.0.199.254/31"
+  }
+}

infrahub/transforms/tests/mlag_yang/spine1/input.json

@@ -0,0 +1,7 @@
+{
+  "data": {
+    "InfraMlagPeerConfig": {
+      "edges": []
+    }
+  }
+}

infrahub/transforms/tests/mlag_yang/spine1/output.json

@@ -0,0 +1 @@
+[]

infrahub/transforms/tests/mlag_yang/test.yml

@@ -0,0 +1,21 @@
+---
+version: "1.0"
+infrahub_tests:
+  - resource: Jinja2Transform
+    resource_name: mlag_yang_transform
+    tests:
+      - name: smoke_check
+        spec:
+          kind: jinja2-transform-smoke
+      - name: render_leaf1
+        spec:
+          kind: jinja2-transform-unit-render
+          directory: infrahub/transforms/tests/mlag_yang/leaf1
+          input: input.json
+          output: output.json
+      - name: render_spine1
+        spec:
+          kind: jinja2-transform-unit-render
+          directory: infrahub/transforms/tests/mlag_yang/spine1
+          input: input.json
+          output: output.json