ignore double team joining

modules/team/src/main/TeamApi.scala

@@ -121,6 +121,8 @@ final class TeamApi(
           ).toFollowersOf(userId).toUsers(previousMembers))
         }
     }
+  } recover {
+    case e: reactivemongo.core.commands.LastError if e.getMessage.contains("duplicate key error") =>
   }
 
   def quit(teamId: String)(implicit ctx: UserContext): Fu[Option[Team]] = for {