fix: missing default value for qos field of API /clients/:clientid/subscribe

apps/emqx_management/src/emqx_mgmt_api_clients.erl

@@ -550,7 +550,7 @@ fields(keepalive) ->
 fields(subscribe) ->
     [
         {topic, hoconsc:mk(binary(), #{desc => <<"Topic">>})},
-        {qos, hoconsc:mk(emqx_schema:qos(), #{desc => <<"QoS">>})},
+        {qos, hoconsc:mk(emqx_schema:qos(), #{default => 0, desc => <<"QoS">>})},
         {nl, hoconsc:mk(integer(), #{default => 0, desc => <<"No Local">>})},
         {rap, hoconsc:mk(integer(), #{default => 0, desc => <<"Retain as Published">>})},
         {rh, hoconsc:mk(integer(), #{default => 0, desc => <<"Retain Handling">>})}