delete notification on user deletion (#658)

* delete notification on user deletion

fix #651

* use the correct id for deletion

* add regression test

* push helpers too

* revert CI changes

plume-models/src/users.rs

@@ -42,6 +42,7 @@ use db_conn::DbConn;
 use follows::Follow;
 use instance::*;
 use medias::Media;
+use notifications::Notification;
 use post_authors::PostAuthor;
 use posts::Post;
 use safe_string::SafeString;
@@ -147,6 +148,10 @@ impl User {
             }
         }
 
+        for notif in Notification::find_followed_by(conn, self)? {
+            notif.delete(conn)?
+        }
+
         diesel::delete(self)
             .execute(conn)
             .map(|_| ())