Set cause on create index request in create from action (elastic#124363)

In the create-index-from-source action, we should set the cause of the create index request so that it is clear in the logs. Without setting the cause on the request, the default value of api is used.

Author: parkertimmins

docs/changelog/124363.yaml

@@ -0,0 +1,5 @@
+pr: 124363
+summary: Set cause on create index request in create from action
+area: Data streams
+type: enhancement
+issues: []

x-pack/plugin/migrate/src/main/java/org/elasticsearch/xpack/migrate/action/CreateIndexFromSourceTransportAction.java

@@ -109,6 +109,7 @@ protected void doExecute(Task task, CreateIndexFromSourceAction.Request request,
         }
 
         var createIndexRequest = new CreateIndexRequest(request.destIndex()).settings(settings);
+        createIndexRequest.cause("create-index-from-source");
         if (mergeMappings.isEmpty() == false) {
             createIndexRequest.mapping(mergeMappings);
         }