chore: use logical pull request commit hash in esignet-mock

Author: naftis

.github/workflows/docker-publish-esignet-mock.yml

@@ -26,6 +26,11 @@ jobs:
     steps:
       - name: Checkout repository
         uses: actions/checkout@v4
+        with:
+          # https://docs.github.com/en/actions/writing-workflows/choosing-when-your-workflow-runs/events-that-trigger-workflows#pull_request
+          # > Note that GITHUB_SHA for this event is the last merge commit of the pull request merge branch.
+          # > If you want to get the commit ID for the last commit to the head branch of the pull request, use _github.event.pull_request.head.sha_ instead.
+          ref: ${{ github.event.pull_request.head.sha || github.ref }}
 
       - name: Log in to the Container registry
         uses: docker/login-action@65b78e6e13532edd9afa3aa52ac7964289d1a9c1