migrate keycloak workflows to forgejo actions

.forgejo/workflows/build_keycloak.yml

@@ -0,0 +1,47 @@
+name: Build Keycloak
+
+on:
+  workflow_dispatch: {}
+  push: {}
+  schedule:
+    - cron: "@daily"
+
+jobs:
+  build-container:
+    name: Build Keycloak Image
+    runs-on: docker
+    container:
+      image: ghcr.io/osscontainertools/kaniko:alpine
+    strategy:
+      matrix:
+         # renovate: datasource=docker depName=quay.io/keycloak/keycloak
+        keycloak-version: [ 26.6.0 ]
+    steps:
+      - name: Install required system packages
+        run: apk add --no-cache nodejs maven git
+
+      - name: Checkout Source Code
+        uses: actions/checkout@v6
+
+      - name: Build attribute-endpoints-provider
+        run: |
+          git clone https://git.hamburg.ccc.de/CCCHH/keycloak-attribute-endpoints-provider.git
+          cd keycloak-attribute-endpoints-provider
+          mvn -f attribute-endpoints-provider verify
+          cp attribute-endpoints-provider/target/attribute-endpoints-provider-1.0-SNAPSHOT.jar ${{ forgejo.workspace }}/keycloak/attribute-endpoints-provider.jar
+
+      - name: Build Container
+        env:
+          KANIKO_NO_PUSH: ${{ forgejo.ref_name != 'main' }}
+          KANIKO_GIT_HAMBURG_CCC_DE_USER: forgejo-actions
+          KANIKO_GIT_HAMBURG_CCC_DE_PASSWORD: ${{ secrets.PACKAGES_TOKEN }}
+        run: /kaniko/executor
+          --dockerfile="${{forgejo.workspace }}/keycloak/Containerfile"
+          --context="dir://${{ forgejo.workspace }}/keycloak"
+          --build-arg=TAG=${{ matrix.keycloak-version }}
+          --destination=git.hamburg.ccc.de/ccchh/oci-images/keycloak:${{ matrix.keycloak-version }}
+          --no-push-cache
+          --credential-helpers=env
+          --annotation=org.opencontainers.image.ref.name=keycloak
+          --annotation=org.opencontainers.image.url=${{ forgejo.server_url }}/${{ forgejo.repository }}
+          --annotation=org.opencontainers.image.source=${{ forgejo.server_url }}/${{ forgejo.repository }}