Add the start time to the repository build object and APIs.

data/database.py

@@ -215,6 +215,8 @@ class RepositoryBuild(BaseModel):
   resource_key = CharField()
   tag = CharField()
   phase = CharField(default='waiting')
+  started = DateTimeField(default=datetime.now)
+
 
 
 class QueueItem(BaseModel):

endpoints/api.py

@@ -1147,6 +1147,7 @@ def build_status_view(build_obj):
   return {
     'id': build_obj.uuid,
     'phase': build_obj.phase,
+    'started': build_obj.started,
     'status': status,
   }