Fix coap uri format (#5059)

apps/emqx_lwm2m/rebar.config

@@ -1,5 +1,5 @@
 {deps,
- [{lwm2m_coap, {git, "https://github.com/emqx/lwm2m-coap", {tag, "v1.1.4"}}}
+ [{lwm2m_coap, {git, "https://github.com/emqx/lwm2m-coap", {tag, "v1.1.5"}}}
  ]}.
 
 {profiles,

apps/emqx_lwm2m/src/emqx_lwm2m_coap_resource.erl

@@ -48,11 +48,11 @@
 -define(LOG(Level, Format, Args), logger:Level("LWM2M-RESOURCE: " ++ Format, Args)).
 
 -dialyzer([{nowarn_function, [coap_discover/2]}]).
-% we use {'absolute', string(), [{atom(), binary()}]} as coap_uri()
+% we use {'absolute', list(binary()), [{atom(), binary()}]} as coap_uri()
 % https://github.com/emqx/lwm2m-coap/blob/258e9bd3762124395e83c1e68a1583b84718230f/src/lwm2m_coap_resource.erl#L61
 % resource operations
 coap_discover(_Prefix, _Args) ->
-    [{absolute, "mqtt", []}].
+    [{absolute, [<<"mqtt">>], []}].
 
 coap_get(ChId, [?PREFIX], Query, Content, Lwm2mState) ->
     ?LOG(debug, "~p ~p GET Query=~p, Content=~p", [self(),ChId, Query, Content]),