[JENKINS-52189] FlowExecutionListener.onCreated

This method is called after the FlowExecution has been created, but before it
is started. This allows to customize the FlowExecution earlier, especially a
GraphListener can be added that also receives the FlowStartNode.

src/main/java/org/jenkinsci/plugins/workflow/flow/FlowExecutionListener.java

@@ -15,6 +15,18 @@
  */
 public abstract class FlowExecutionListener implements ExtensionPoint {
 
+    /**
+     * Called when a {@link FlowExecution} has been created, but before it starts running.
+     *
+     * The {@link FlowExecution} will already have been added to the {@link FlowExecutionList} by this point.
+     * Methods relating to in-progress execution state such as {@link FlowExecution#getCurrentHeads}
+     * will not work as intended and should not be used.
+     *
+     * @param execution The {@link FlowExecution} that has been created.
+     */
+    public void onCreated(@Nonnull FlowExecution execution) {
+    }
+
     /**
      * Called when a {@link FlowExecution} has started running.
      *
@@ -46,6 +58,15 @@ public void onResumed(@Nonnull FlowExecution execution) {
     public void onCompleted(@Nonnull FlowExecution execution) {
     }
 
+    /**
+     * Fires the {@link #onCreated(FlowExecution)} event.
+     */
+    public static void fireCreated(@Nonnull FlowExecution execution) {
+        for (FlowExecutionListener listener : ExtensionList.lookup(FlowExecutionListener.class)) {
+            listener.onCreated(execution);
+        }
+    }
+
     /**
      * Fires the {@link #onRunning(FlowExecution)} event.
      */