litrpc: add macaroon_identifier to Action message

We add a new macaroon_identifier field to the Action proto message an
populate it in the rpc server.

Author: ellemouton

litrpc/firewall.pb.go

@@ -209,6 +209,12 @@ message Action {
     The ID of the session under which the action was performed.
     */
     bytes session_id = 11;
+
+    /*
+    The 4 byte identifier of the macaroon that was used to perform the action.
+    This is derived from the last 4 bytes of the macaroon's root key ID.
+    */
+    bytes macaroon_identifier = 12;
 }
 
 enum ActionState {

litrpc/firewall.proto

@@ -132,6 +132,11 @@
           "type": "string",
           "format": "byte",
           "description": "The ID of the session under which the action was performed."
+        },
+        "macaroon_identifier": {
+          "type": "string",
+          "format": "byte",
+          "description": "The 4 byte identifier of the macaroon that was used to perform the action.\nThis is derived from the last 4 bytes of the macaroon's root key ID."
         }
       }
     },

litrpc/firewall.swagger.json

@@ -738,6 +738,7 @@ func (s *sessionRpcServer) ListActions(ctx context.Context,
 
 		resp[i] = &litrpc.Action{
 			SessionId:          sessionID[:],
+			MacaroonIdentifier: a.MacaroonIdentifier[:],
 			ActorName:          a.ActorName,
 			FeatureName:        a.FeatureName,
 			Trigger:            a.Trigger,