Commit the Ubuntu support matrix automatically

Fixes #10

.github/workflows/build-and-push.yaml

@@ -10,13 +10,22 @@ on:
   workflow_dispatch:
 
 jobs:
-  build_push_images:
+  get-ubuntu-versions:
     runs-on: ubuntu-latest
+    outputs:
+      versions: ${{ steps.versions.outputs.versions }}
+    steps:
+      - name: Query Launchpad API for active and supported Ubuntu versions
+        id: versions
+        # This command actually grabs Ubuntu ESM-supported releases too, but the Launchpad API doesn't give a way to differentiate these out so who cares
+        run: curl https://api.launchpad.net/devel/ubuntu/series | jq '.entries[] | select(.supported == true and .active == true) | .version' | tr '\n' ' ' | sed -e 's/^/versions=[/' -e 's/ $/]/' -e 's/ /, /g' >> "$GITHUB_OUTPUT"
+
+  build-push-images:
+    runs-on: ubuntu-latest
+    needs: get-ubuntu-versions
     strategy:
       matrix:
-        # curl https://api.launchpad.net/devel/ubuntu/series | jq '.entries[] | select(.supported == true and .active == true) | .version' | tr '\n' ' ' | sed -e 's/^/[/' -e 's/ $/]/' -e 's/ /, /g'
-        # The above command actually grabs Ubuntu ESM-supported releases too, but the Launchpad API doesn't give a way to differentiate these out so who cares
-        version: ["24.04", "22.04", "20.04", "18.04", "16.04", "14.04"]
+        version: ${{ fromJSON(needs.get-ubuntu-versions.outputs.versions }}
     env:
       REGISTRY_USER: ${{ github.actor }}
       REGISTRY_PASSWORD: ${{ github.token }}