CI: add simple Azure Login workflow

We currently depend on the azure/login GitHub Action in various places. It simply runs an "az login" and "az account set" behind the scenes, and has support for plenty of other scenarios.

As we're moving away from azure/cli in more and more places, we could also replace the login script with our own. Let's create a Composite Workflow to achieve this goal.

Signed-off-by: Dennis Ameling <dennis@dennisameling.com>

Author: dennisameling

.github/workflows/azure-login/action.yml

@@ -0,0 +1,43 @@
+name: Azure Login
+description: Logs into Azure using a service principal
+inputs:
+  credentials:
+    description: Your credentials in JSON format
+    required: true
+
+runs:
+  using: "composite"
+  steps:
+    - name: Process Azure credentials
+      uses: actions/github-script@v7
+      env:
+        AZURE_CREDENTIALS: ${{ inputs.credentials }}
+      with:
+        script: |
+          if (!process.env.AZURE_CREDENTIALS) {
+            core.setFailed('The AZURE_CREDENTIALS secret is required.')
+            process.exit(1)
+          }
+          
+          const azureCredentials = JSON.parse(process.env.AZURE_CREDENTIALS)
+          const {clientId, clientSecret, tenantId, subscriptionId} = azureCredentials
+
+          core.setSecret(clientId)
+          core.exportVariable('AZURE_CLIENT_ID', clientId)
+
+          core.setSecret(clientSecret)
+          core.exportVariable('AZURE_CLIENT_SECRET', clientSecret)
+
+          core.setSecret(tenantId)
+          core.exportVariable('AZURE_TENANT_ID', tenantId)
+
+          core.setSecret(subscriptionId)
+          core.exportVariable('AZURE_SUBSCRIPTION_ID', subscriptionId)
+    
+    - name: Azure Login
+      shell: bash
+      run: |
+        echo "Logging into Azure..."
+        az login --service-principal -u ${{ env.AZURE_CLIENT_ID }} -p ${{ env.AZURE_CLIENT_SECRET }} --tenant ${{ env.AZURE_TENANT_ID }}
+        echo "Setting subscription..."
+        az account set --subscription ${{ env.AZURE_SUBSCRIPTION_ID }} --output none