feat: adds workflow to publish container image to GHCR

Refs: PSCE-199

Signed-off-by: Jennifer Power <[email protected]>

.github/workflows/publish.yml

@@ -0,0 +1,71 @@
+name: Publish Image to GHCR
+
+on:
+  release:
+    types: [published]
+  workflow_dispatch:
+    inputs:
+      tag:
+        description: "Name of the tag for the published image"
+        type: string
+        required: true
+env:
+    IMAGE_NAME: trestle-bot
+    IMAGE_REGISTRY: ghcr.io/redhatproductsecurity
+
+jobs:
+  publish-image:
+    runs-on: 'ubuntu-latest'
+    permissions:
+      contents: read
+      packages: write
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v3
+
+      - name: Log in to ghcr.io
+        uses: redhat-actions/podman-login@v1
+        with:
+          username: ${{ github.actor }}
+          password: ${{ secrets.GITHUB_TOKEN }}
+          registry: ${{ env.IMAGE_REGISTRY }}
+
+      - name: Check if triggered by release or workflow dispatch
+        id: check_event
+        run: echo ::set-output name=event_type::${{ toJson(github.event_name) }}
+
+      # Using intermediary variable to process event based input
+      - name: Set TAG environment variable for Release
+        if: steps.check_event.outputs.event_type == 'release'
+        run: echo "TAG=${RELEASE_VERSION}" >> $GITHUB_ENV
+        env:
+          RELEASE_VERSION: ${{ github.event.release.tag_name }}
+
+      - name: Set TAG environment variable for Workflow Dispatch
+        if: steps.check_event.outputs.event_type == 'workflow_dispatch'
+        run: echo "TAG=${INPUT_VERSION}" >> $GITHUB_ENV
+        env:
+          INPUT_VERSION: ${{ github.event.inputs.tag }}
+
+      - name: Build image with Buildah
+        id: build-image
+        uses: redhat-actions/buildah-build@v2
+        with:
+          image:  ${{ env.IMAGE_NAME }}
+          tags: ${{ env.TAG }}
+          containerfiles: |
+            ./Dockerfile
+        
+      - name: Push To GHCR
+        uses: redhat-actions/push-to-registry@v2
+        id: push
+        with:
+          image: ${{ steps.build_image.outputs.image }}
+          tags: ${{ steps.build_image.outputs.tags }}
+          registry: ${{ env.IMAGE_REGISTRY }}
+
+      - name: Echo outputs
+        run: |
+          echo "${{ toJSON(steps.push.outputs) }}"
+
+