ci: build nightly OCI image

It's a middle ground between building on every commit, and not building
at all. We currently have a workflow to build the OCI on every PR.
However, building on every PR does not cover some use cases. For
example, providing an image to a user to preview some changes coming in
the next minor or patch. Another use case: compare main with a PR in
Kubernetes.

It's better to have a separate workflow, even at the expense of
duplication, because the "on schedule" trigger only runs on the default
branch of the repository. This "limitation" makes it complicated to
extend the current "build OCI on PRs" to also build nightly for main and
release branches.

Author: Zerpet

.github/workflows/oci-make-nightly.yaml

@@ -0,0 +1,117 @@
+name: Nightly OCI (make)
+on:
+  schedule:
+    # at 2:20am Mon-Fri
+    # GitHub advises to schedule jobs NOT at the start of the hour
+    # https://docs.github.com/en/actions/writing-workflows/choosing-when-your-workflow-runs/events-that-trigger-workflows#schedule
+    - cron: 20 2 * * 1-5
+env:
+  REGISTRY_IMAGE: pivotalrabbitmq/rabbitmq
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
+jobs:
+  build-package-generic-unix:
+    strategy:
+      matrix:
+        otp_version:
+          - '27'
+        branch:
+          - main
+          - v4.1.x
+          - v4.0.x
+
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+        with:
+          ref: ${{ matrix.branch }}
+
+      - name: Configure Erlang
+        uses: erlef/setup-beam@v1
+        with:
+          otp-version: ${{ matrix.otp_version }}
+          elixir-version: latest
+
+      - name: make package-generic-unix
+        id: make
+        run: |
+          make package-generic-unix PROJECT_VERSION=${{ matrix.branch }}+${{ github.sha }}
+
+      - name: Upload package-generic-unix
+        uses: actions/upload-artifact@v4
+        with:
+          name: package-generic-unix-otp${{ matrix.otp_version }}-${{ matrix.branch }}
+          path: PACKAGES/rabbitmq-server-*.tar.xz
+
+  build-and-push:
+    strategy:
+      fail-fast: false
+      matrix:
+        otp_version:
+          - '27'
+        branch:
+          - main
+          - v4.1.x
+          - v4.0.x
+
+    needs: build-package-generic-unix
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+        with:
+          ref: ${{ matrix.branch }}
+
+      - name: Download package-generic-unix
+        uses: actions/download-artifact@v4
+        with:
+          name: package-generic-unix-otp${{ matrix.otp_version }}-${{ matrix.branch }}
+          path: PACKAGES
+
+      - name: Rename package-generic-unix
+        run: |
+          cp \
+            PACKAGES/rabbitmq-server-generic-unix-*.tar.xz \
+            packaging/docker-image/package-generic-unix.tar.xz
+
+      - name: Docker meta
+        id: meta
+        uses: docker/metadata-action@v5
+        with:
+          images: ${{ env.REGISTRY_IMAGE }}
+          flavor: |
+            suffix=-otp${{ matrix.otp_version }}
+          tags: |
+            type=sha,format=long
+            type=schedule,pattern=nightly.{{date 'YYYYMMDD'}},prefix=${{ matrix.branch }}+
+
+      - name: Set up QEMU
+        uses: docker/setup-qemu-action@v3
+
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v3
+
+      - name: Login to Docker Hub
+        uses: docker/login-action@v3
+        with:
+          username: ${{ secrets.DOCKERHUB_USERNAME }}
+          password: ${{ secrets.DOCKERHUB_PASSWORD }}
+
+      - name: Build and push by digest
+        id: build
+        uses: docker/build-push-action@v6
+        with:
+          push: true
+          context: packaging/docker-image
+          labels: ${{ steps.meta.outputs.labels }}
+          platforms: linux/amd64
+          tags: ${{ steps.meta.outputs.tags }}
+          cache-to: type=gha,mode=max,scope=${{ matrix.otp_version }}
+          cache-from: type=gha,scope=${{ matrix.otp_version }}
+          build-args: |
+            OTP_VERSION=${{ matrix.otp_version }}
+            RABBITMQ_VERSION=${{ matrix.branch }}+${{ github.sha }}