[+] add function GetSubscriberByUser for the agenda-widget

grpcapi/agenda.proto

@@ -17,6 +17,7 @@ service Agenda {
     rpc SubscribeEvent(SubscribeEventRequest) returns (SubscribeEventResponse) {}
     rpc UnsubscribeEvent(UnsubscribeEventRequest) returns (UnsubscribeEventResponse) {}
     rpc DeleteSubscription(DeleteSubscriptionRequest) returns (DeleteSubscriptionResponse) {}
+    rpc GetSubscriptionByUser(GetSubscriptionByUserRequest) returns (GetSubscriptionByUserResponse) {}
 }
 
 message CreateEventRequest {
@@ -88,4 +89,12 @@ message UpdateEventRequest {
 
 message UpdateEventResponse {
     Event event = 53;
-}
+}
+
+message GetSubscriptionByUserRequest {
+    string subscriber = 54;
+}
+
+message GetSubscriptionByUserResponse {
+    repeated Subscription subscription = 55;
+}