CI: add publish_charm workflow (#1909)

.github/workflows/publish_charm.yaml

@@ -0,0 +1,40 @@
+name: Build and publish charm
+on:
+  push:
+    branches:
+      - charming-charmhub # TODO(mhdisk): Change this to main once we are ready to deploy
+env:
+  CHARMCRAFT_ENABLE_EXPERIMENTAL_EXTENSIONS: true
+  ROCKCRAFT_ENABLE_EXPERIMENTAL_EXTENSIONS: true
+
+jobs:
+  upload-charm:
+    name: Build and upload charm to charmhub
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Setup LXD
+        uses: canonical/setup-lxd@main
+
+      - name: Setup Charmcraft
+        run: |
+          sudo snap install charmcraft --classic --channel=latest/edge
+          sudo snap install rustup --classic
+
+      - name: Fetch charm libs
+        run: |
+          cd ./charm
+          charmcraft fetch-libs
+      - name: Pack charm
+        run: |
+          mkdir dist
+          charmcraft pack -v --project-dir ./charm -o dist
+      - name: Upload charm to charmhub
+        uses: canonical/charming-actions/[email protected]
+        with:
+          charm-path: ./charm/
+          credentials: ${{ secrets.CHARMHUB_TOKEN }}
+          github-token: ${{ secrets.GITHUB_TOKEN }}
+          charmcraft-channel: latest/edge
+          built-charm-path: ./dist/