ci: post diff as comment on PRs that modify vocdoni-api.yaml

.github/workflows/swagger.yml

@@ -34,6 +34,29 @@ jobs:
           cmd: |
             yq '.components.schemas."api.GenericTransactionWithInfo".properties.tx = load("api/docs/models/transactions.yaml").target' \
               api/docs/oas3.yaml > api/docs/vocdoni-api.yaml
+
+      - name: Fetch upstream vocdoni-api.yaml
+        run: |
+          git add api/docs/vocdoni-api.yaml
+          curl -o api/docs/vocdoni-api.yaml https://raw.githubusercontent.com/vocdoni/developer-portal/main/swaggers/vocdoni-api.yaml
+
+      - name: Check if there is a difference
+        uses: mathiasvr/[email protected]
+        id: diff
+        with:
+          run: git diff --color api/docs/vocdoni-api.yaml
+
+      - name: Post PR comment with diff
+        if: ${{ steps.diff.outputs.stdout }}
+        uses: marocchino/sticky-pull-request-comment@v2
+        with:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+          header: "This PR introduces the following changes in the developer-portal documentation:"
+          message: |
+            ```diff
+            ${{ steps.diff.outputs.stdout }}
+            ```
+
       - name: Publish Artifact
         uses: actions/upload-artifact@v4
         with: