Add independent dev container build job and new verify job

.github/workflows/devcontainer.yml

@@ -7,10 +7,11 @@ on: # rebuild any PRs and main branch changes
       - benchmarking
 
 jobs:
-  build:
+  build-devcontainer:
     runs-on: ubuntu-latest
+    outputs:
+      imageName: ${{ steps.imageName.outputs.imageName }}
     steps:
-
       - name: Checkout (GitHub)
         uses: actions/checkout@v3
 
@@ -22,15 +23,61 @@ jobs:
           password: ${{ secrets.GITHUB_TOKEN }}
 
       - name: set lower case owner name
+        id: imageName
         run: |
             echo "OWNER_LC=${OWNER,,}" >>${GITHUB_ENV}
+            echo "imageName=ghcr.io/{OWNER,,}/r-compile-server" >>${GITHUB_OUTPUT}
         env:
             OWNER: '${{ github.repository_owner }}'
+
+      - name: Pre-build dev container image
+        uses: devcontainers/[email protected]
+        with:
+          imageName: ghcr.io/${{ env.OWNER_LC }}/r-compile-server
+          cacheFrom: ghcr.io/${{ env.OWNER_LC }}/r-compile-server
+          push: always
+  test:
+    runs-on: ubuntu-latest
+    needs: build-devcontainer
+    steps:
+
+      - name: Checkout (GitHub)
+        uses: actions/checkout@v3
+
+      - name: Login to GitHub Container Registry
+        uses: docker/login-action@v2 
+        with:
+          registry: ghcr.io
+          username: ${{ github.repository_owner }}
+          password: ${{ secrets.GITHUB_TOKEN }}
+
 
       # See https://github.com/devcontainers/ci/blob/main/docs/github-action.md
       - name: Build and run dev container task
         uses: devcontainers/[email protected]
         with:
-          imageName: ghcr.io/${{ env.OWNER_LC }}/r-compile-server
+          cacheFrom:  ${{ needs.build-devcontainer.outputs.imageName }}
           # Change this to be your CI task/script
-          runCmd: cd server; mvn --batch-mode --update-snapshots test
+          runCmd: cd server; mvn --batch-mode --update-snapshots test
+
+  verify:
+    runs-on: ubuntu-latest
+    needs: build-devcontainer
+    steps:
+
+      - name: Checkout (GitHub)
+        uses: actions/checkout@v3
+
+      - name: Login to GitHub Container Registry
+        uses: docker/login-action@v2 
+        with:
+          registry: ghcr.io
+          username: ${{ github.repository_owner }}
+          password: ${{ secrets.GITHUB_TOKEN }}
+
+
+      - name: Build and run dev container task
+        uses: devcontainers/[email protected]
+        with:
+          cacheFrom:  ${{ needs.build-devcontainer.outputs.imageName }}
+          runCmd: cd server; mvn --batch-mode --update-snapshots verify