feat: Add Infrahub Jinja2 transform for VRF/L3VNI configuration (#21) (#25)

## Summary

Implements Infrahub Jinja2 Transform for VRF/L3VNI configuration, generating structured JSON payloads from Infrahub intent data. Closes #21.

## What's included

- **GraphQL query** (`transforms/queries/vrf_intent.gql`): Queries `InfraVRFDeviceAssignment` by device name, fetching VRF details, L3VNI, route targets, and device-specific route distinguisher
- **Jinja2 transform** (`transforms/templates/vrf_yang.j2`): Renders VRF config payloads with defensive null handling (lessons learned from #20)
- **`.infrahub.yml`** updated with the new query and transform definitions
- **Tests** (`transforms/tests/vrf_yang/`) using correct Infrahub pytest format (`jinja2-transform-smoke` + `jinja2-transform-unit-render`)

## Validation

All transforms render correctly:

| Device | Expected | Result |
|--------|----------|--------|
| `leaf3` | VRF gold, RD `10.0.250.13:1`, L3VNI 100001 | ✅ |
| `leaf7` | VRF gold, RD `10.0.250.17:1`, L3VNI 100001 | ✅ |
| `leaf1` | Empty array (no VRF assignment) | ✅ |
| `spine1` | Empty array (no VRF assignment) | ✅ |

## Usage

```bash
# Local debugging
infrahubctl render vrf_yang_transform device_name=leaf3

# API endpoint
GET /api/transform/jinja2/vrf_yang_transform?device_name=leaf3
```

## Related

- Depends on: #20 (base transforms infrastructure, already merged)
- Reference: Arista EVPN Type-5 / L3VXLAN configuration from lab topology

.infrahub.yml

@@ -24,6 +24,8 @@ queries:
     file_path: infrahub/transforms/queries/interface_intent.gql
   - name: vxlan_intent
     file_path: infrahub/transforms/queries/vxlan_intent.gql
+  - name: vrf_intent
+    file_path: infrahub/transforms/queries/vrf_intent.gql
 
 jinja2_transforms:
   - name: vlan_yang_transform
@@ -38,3 +40,7 @@ jinja2_transforms:
     description: "Generate VXLAN/VTEP configuration payload from Infrahub intent"
     query: vxlan_intent
     template_path: infrahub/transforms/templates/vxlan_yang.j2
+  - name: vrf_yang_transform
+    description: "Generate VRF/L3VNI configuration payload from Infrahub intent"
+    query: vrf_intent
+    template_path: infrahub/transforms/templates/vrf_yang.j2

infrahub/transforms/queries/vrf_intent.gql

@@ -0,0 +1,50 @@
+query VrfIntent($device_name: String!) {
+  InfraVRFDeviceAssignment(device__name__value: $device_name) {
+    edges {
+      node {
+        route_distinguisher { value }
+        vrf {
+          node {
+            name { value }
+            description { value }
+            route_distinguisher { value }
+            l3vni {
+              node {
+                vni { value }
+                vni_type { value }
+              }
+            }
+            import_targets {
+              edges {
+                node {
+                  target { value }
+                }
+              }
+            }
+            export_targets {
+              edges {
+                node {
+                  target { value }
+                }
+              }
+            }
+          }
+        }
+        import_targets {
+          edges {
+            node {
+              target { value }
+            }
+          }
+        }
+        export_targets {
+          edges {
+            node {
+              target { value }
+            }
+          }
+        }
+      }
+    }
+  }
+}

infrahub/transforms/templates/vrf_yang.j2

@@ -0,0 +1,78 @@
+{#
+  vrf_yang.j2 — Produce a JSON array of VRF configuration objects.
+
+  Input: GraphQL response from vrf_intent query.
+  For each VRFDeviceAssignment, produce one VRF config entry with:
+    - device-specific RD (falls back to VRF-level RD if not set on assignment)
+    - L3VNI from the VRF's l3vni relationship
+    - import/export targets: device-level if present, otherwise VRF-level
+#}
+{%- set vrf_list = [] -%}
+
+{%- for assignment_edge in data.InfraVRFDeviceAssignment.edges -%}
+  {%- set assignment = assignment_edge.node -%}
+
+  {#— Resolve VRF node —#}
+  {%- set vrf_name = none -%}
+  {%- set vrf_description = none -%}
+  {%- set l3vni = none -%}
+  {%- set vrf_level_import_rts = [] -%}
+  {%- set vrf_level_export_rts = [] -%}
+
+  {%- if assignment.vrf is defined and assignment.vrf is not none and assignment.vrf.node is not none -%}
+    {%- set vrf_node = assignment.vrf.node -%}
+    {%- set vrf_name = vrf_node.name.value -%}
+    {%- set vrf_description = vrf_node.description.value | default(none) -%}
+
+    {%- if vrf_node.l3vni is defined and vrf_node.l3vni is not none and vrf_node.l3vni.node is not none -%}
+      {%- set l3vni = vrf_node.l3vni.node.vni.value -%}
+    {%- endif -%}
+
+    {%- for rt_edge in vrf_node.import_targets.edges -%}
+      {%- set _ = vrf_level_import_rts.append(rt_edge.node.target.value) -%}
+    {%- endfor -%}
+    {%- for rt_edge in vrf_node.export_targets.edges -%}
+      {%- set _ = vrf_level_export_rts.append(rt_edge.node.target.value) -%}
+    {%- endfor -%}
+  {%- endif -%}
+
+  {#— Resolve route_distinguisher: device-specific first, fall back to VRF-level —#}
+  {%- set rd = none -%}
+  {%- if assignment.route_distinguisher is defined and assignment.route_distinguisher is not none and assignment.route_distinguisher.value is not none and assignment.route_distinguisher.value != "" -%}
+    {%- set rd = assignment.route_distinguisher.value -%}
+  {%- elif assignment.vrf is defined and assignment.vrf is not none and assignment.vrf.node is not none and assignment.vrf.node.route_distinguisher is defined and assignment.vrf.node.route_distinguisher is not none -%}
+    {%- set rd = assignment.vrf.node.route_distinguisher.value | default(none) -%}
+  {%- endif -%}
+
+  {#— Resolve import targets: device-level if present, otherwise VRF-level —#}
+  {%- set import_rts = [] -%}
+  {%- if assignment.import_targets is defined and assignment.import_targets is not none and assignment.import_targets.edges | length > 0 -%}
+    {%- for rt_edge in assignment.import_targets.edges -%}
+      {%- set _ = import_rts.append(rt_edge.node.target.value) -%}
+    {%- endfor -%}
+  {%- else -%}
+    {%- set import_rts = vrf_level_import_rts -%}
+  {%- endif -%}
+
+  {#— Resolve export targets: device-level if present, otherwise VRF-level —#}
+  {%- set export_rts = [] -%}
+  {%- if assignment.export_targets is defined and assignment.export_targets is not none and assignment.export_targets.edges | length > 0 -%}
+    {%- for rt_edge in assignment.export_targets.edges -%}
+      {%- set _ = export_rts.append(rt_edge.node.target.value) -%}
+    {%- endfor -%}
+  {%- else -%}
+    {%- set export_rts = vrf_level_export_rts -%}
+  {%- endif -%}
+
+  {%- set _ = vrf_list.append({
+    "vrf_name": vrf_name,
+    "description": vrf_description,
+    "route_distinguisher": rd,
+    "l3vni": l3vni,
+    "import_targets": import_rts,
+    "export_targets": export_rts,
+    "redistribute_connected": true
+  }) -%}
+{%- endfor -%}
+
+{{ vrf_list | tojson(indent=2) }}

infrahub/transforms/tests/vrf_yang/input.json

@@ -0,0 +1,82 @@
+{
+  "data": {
+    "InfraVRFDeviceAssignment": {
+      "edges": [
+        {
+          "node": {
+            "route_distinguisher": {
+              "value": "10.0.250.13:1"
+            },
+            "vrf": {
+              "node": {
+                "name": {
+                  "value": "gold"
+                },
+                "description": {
+                  "value": "VRF gold - L3 VXLAN with symmetric IRB"
+                },
+                "route_distinguisher": {
+                  "value": null
+                },
+                "l3vni": {
+                  "node": {
+                    "vni": {
+                      "value": 100001
+                    },
+                    "vni_type": {
+                      "value": "l3vni"
+                    }
+                  }
+                },
+                "import_targets": {
+                  "edges": [
+                    {
+                      "node": {
+                        "target": {
+                          "value": "1:100001"
+                        }
+                      }
+                    }
+                  ]
+                },
+                "export_targets": {
+                  "edges": [
+                    {
+                      "node": {
+                        "target": {
+                          "value": "1:100001"
+                        }
+                      }
+                    }
+                  ]
+                }
+              }
+            },
+            "import_targets": {
+              "edges": [
+                {
+                  "node": {
+                    "target": {
+                      "value": "1:100001"
+                    }
+                  }
+                }
+              ]
+            },
+            "export_targets": {
+              "edges": [
+                {
+                  "node": {
+                    "target": {
+                      "value": "1:100001"
+                    }
+                  }
+                }
+              ]
+            }
+          }
+        }
+      ]
+    }
+  }
+}

infrahub/transforms/tests/vrf_yang/output.json

@@ -0,0 +1,15 @@
+[
+  {
+    "description": "VRF gold - L3 VXLAN with symmetric IRB",
+    "export_targets": [
+      "1:100001"
+    ],
+    "import_targets": [
+      "1:100001"
+    ],
+    "l3vni": 100001,
+    "redistribute_connected": true,
+    "route_distinguisher": "10.0.250.13:1",
+    "vrf_name": "gold"
+  }
+]

infrahub/transforms/tests/vrf_yang/test.yml

@@ -0,0 +1,15 @@
+---
+version: "1.0"
+infrahub_tests:
+  - resource: Jinja2Transform
+    resource_name: vrf_yang_transform
+    tests:
+      - name: smoke_check
+        spec:
+          kind: jinja2-transform-smoke
+      - name: render_leaf3
+        spec:
+          kind: jinja2-transform-unit-render
+          directory: infrahub/transforms/tests/vrf_yang
+          input: input.json
+          output: output.json