Add update_time field to Dispatch object

Signed-off-by: Stefan Brus <[email protected]>

Author: stefan-brus-frequenz

RELEASE_NOTES.md

@@ -1,3 +1,4 @@
 # Release notes
 
 - The field `create_time` has been removed from update requests.
+- An `update_time` field has been added to the Dispatch object.

proto/frequenz/api/dispatch/dispatch.proto

@@ -77,6 +77,10 @@ message Dispatch {
   // The creation time
   // This is set when a dispatch is created via the create request message
   google.protobuf.Timestamp create_time = 10;
+
+  // The update time
+  // This is set when a dispatch is modified via the update request message
+  google.protobuf.Timestamp update_time = 11;
 }
 
 // Filter parameter for specifying multiple time intervals