build: add workflow to explicitly trigger EDC jenkins (#56)

.github/workflows/trigger_snapshot.yml

@@ -0,0 +1,31 @@
+name: "Create Snapshot Build"
+
+on:
+  push:
+    branches:
+      - main
+
+jobs:
+  Trigger-Snapshot:
+    runs-on: ubuntu-latest
+    steps:
+      # Trigger EF Jenkins. This job waits for Jenkins to complete the publishing, which may take a long time, because every
+      # module is signed individually, and parallelism is not available. Hence, the increased timeout of 3600 seconds.
+      # There is no way to cancel the process on Jenkins from withing GitHub.
+      - name: Call Jenkins API to trigger build
+        id: runjenkins
+        uses: toptal/jenkins-job-trigger-action@master
+        with:
+          jenkins_url: "https://ci.eclipse.org/dataspaceconnector/"
+          jenkins_user: ${{ secrets.EF_JENKINS_USER }}
+          jenkins_token: ${{ secrets.EF_JENKINS_TOKEN }}
+          # empty params are needed, otherwise the job will fail.
+          job_params: |
+            {
+            }
+          job_name: "GradlePlugins-Snapshot"
+          job_timeout: "3600" # Default 30 sec. (optional)
+
+      - name: Log Jenkins URL
+        run:
+          echo "::notice title=Jenkins URL::${{ steps.runjenkins.outputs.jenkins_job_url }} "