anchor.diff:  options(Req0, State) ->
       %% CORS Headers
       Req1 = cowboy_req:set_resp_header(<<"access-control-max-age">>, <<"1728000">>, Req0),
  -    Req2 = cowboy_req:set_resp_header(<<"access-control-allow-methods">>, <<"HEAD, GET, POST">>, Req1),
  +    Req2 = cowboy_req:set_resp_header(<<"access-control-allow-methods">>, <<"HEAD, GET">>, Req1),
       Req3 = cowboy_req:set_resp_header(<<"access-control-allow-headers">>, <<"content-type, authorization">>, Req2),
       Req4 = cowboy_req:set_resp_header(<<"access-control-allow-origin">>, <<$*>>, Req3),
   
  
positive.code:     ApiKey.
  
  delete_api_key(ApiKey) ->
      case vmq_config:get_env(vmq_server, ?ENV_API_KEYS) of
          undefined -> ok;
          Keys when is_list(Keys) ->
              vmq_config:set_global_env(vmq_server, ?ENV_API_KEYS, Keys -- [ApiKey], true)
  
negative.code:     {ok, Req, undefined}.
  
  allowed_methods(Req, State) ->
      {[<<"GET">>, <<"OPTIONS">>, <<"HEAD">>], Req, State}.
  
  content_types_provided(Req, State) ->
      {[{<<"application/json">>, to_json}], Req, State}.
  