Only run a single release workflow at the same time

.github/workflows/release.yml

@@ -16,6 +16,11 @@ on:
         type: string
         description: Set an explicit version, that will overwrite release-type. Fails if version is not compliant.
 
+# don't run two release processes at the same time
+# but also don't cancel already running workflow because it might already be to late
+concurrency:
+  group: ${{ github.workflow }}
+
 jobs:
   build-and-release:
     name: Create a new release with pontos