fix: require calendar owner or admin for booking confirm/decline. Fixes EventHub/EventHubBack#53

src/handlers/handler_booking_by_id.erl

@@ -64,6 +64,7 @@ trails() ->
       responses => #{
         200 => #{description => <<"Booking updated">>},
         400 => #{description => <<"Invalid action">>},
+        403 => #{description => <<"Access denied">>},
         404 => #{description => <<"Booking not found">>}
       }
     },