feat: add github workflow for building docker images from main branch (#5517)

Author: avrittrohwer

.github/workflows/docker_image_build.yml

@@ -0,0 +1,60 @@
+name: Docker Image Build
+
+on:
+  push:
+    branches:
+      - main
+  workflow_dispatch:
+
+permissions:
+  contents: read
+  packages: write
+
+env:
+  image_base: ghcr.io/${{ github.repository }}
+
+jobs:
+  build-image:
+    # Builds each image in a separate job in parallel.
+    strategy:
+      matrix:
+        # The docker/build-push-action uses the git repo as the docker build context instead of
+        # cloning the repo to the action runner disk and using the disk context. For the API image
+        # we need to set the context to just the api/ directory which the '{{defaultContext}}:api'
+        # syntax does: https://github.com/docker/build-push-action?tab=readme-ov-file#git-context.
+        include:
+          - container: api
+            docker_context: "{{defaultContext}}:api"
+            dockerfile: Dockerfile
+          - container: partners
+            docker_context: "{{defaultContext}}"
+            dockerfile: Dockerfile.sites.partners
+          - container: public
+            docker_context: "{{defaultContext}}"
+            dockerfile: Dockerfile.sites.public
+    runs-on: ubuntu-latest
+    steps:
+      - name: Log in to GitHub Container Registry
+        uses: docker/login-action@v3.6.0
+        with:
+          registry: ghcr.io
+          username: ${{ github.actor }}
+          password: ${{ secrets.GITHUB_TOKEN }}
+
+      # Required to use image layer cache.
+      - name: Setup Docker Buildx
+        uses: docker/setup-buildx-action@v3.11.1
+
+      - name: "Build and push image"
+        uses: docker/build-push-action@v6.18.0
+        with:
+          push: true
+          cache-to: type=registry,mode=max,ref=${{ env.image_base }}/${{ matrix.container }}/container-layer-cache:latest
+          cache-from: type=registry,ref=${{ env.image_base }}/${{ matrix.container }}/container-layer-cache:latest
+          context: ${{ matrix.docker_context }}
+          file: ${{ matrix.dockerfile }}
+          tags: |
+            ${{ env.image_base }}/${{ matrix.container }}:latest
+            ${{ env.image_base }}/${{ matrix.container }}:gitsha-${{ github.sha }}
+          # Connects the image to the repository: https://docs.github.com/en/packages/learn-github-packages/connecting-a-repository-to-a-package.
+          labels: org.opencontainers.image.source=https://github.com/${{ github.repository }}