chore: use github action to terraform plan

Author: jgravois

.github/workflows/terraform-plan.yml

@@ -0,0 +1,46 @@
+name: Terraform plan
+
+# TODO: only run when the contents of terraform/ have changed
+on:
+  workflow_dispatch:
+  pull_request:
+
+environment:
+  name: "dev"
+
+# Federated Identity credentials
+permissions:
+  id-token: write
+  contents: read
+
+jobs:
+  terraform-plan:
+    runs-on: ubuntu-latest
+    defaults:
+      run:
+        working-directory: infra/terraform
+
+    steps:
+      - name: Check out the repository
+        uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7
+
+      - name: Log in to azure using federated identity credentials
+        uses: azure/login@532459ea530d8321f2fb9bb10d1e0bcf23869a43 # v3
+        with:
+          client-id: ${{ secrets.AZURE_SP_PR_CLIENT_ID }}
+          tenant-id: ${{ secrets.AZURE_SP_TENANT_ID }}
+          subscription-id: ${{ secrets.AZURE_SP_SUBSCRIPTION_ID }}
+
+      - name: Setup terraform
+        uses: hashicorp/setup-terraform@dfe3c3f87815947d99a8997f908cb6525fc44e9e # v4
+        with:
+          terraform_version: 1.14.5
+
+      - name: Initialize terraform and select workspace
+        run: terraform/init.sh dev
+
+      - name: Terraform Plan
+        run: |
+          cd terraform && \
+            terraform plan \
+            -var "CONTAINER_TAG=${{ github.sha }}" \