implement labels for workflows JT and workflow jobs

awx/api/views.py

@@ -2726,6 +2726,11 @@ class WorkflowJobTemplateDetail(RetrieveUpdateDestroyAPIView):
     serializer_class = WorkflowJobTemplateSerializer
     always_allow_superuser = False
 
+
+class WorkflowJobTemplateLabelList(JobTemplateLabelList):
+    parent_model = WorkflowJobTemplate
+
+
 # TODO:
 class WorkflowJobTemplateLaunch(GenericAPIView):
 
@@ -2883,6 +2888,9 @@ class JobLabelList(SubListAPIView):
     relationship = 'labels'
     parent_key = 'job'
 
+class WorkflowJobLabelList(JobLabelList):
+    parent_model = WorkflowJob
+
 class JobActivityStreamList(SubListAPIView):
 
     model = ActivityStream