uses a better approach than before to dynamically pick the api key an…

…d secret key.

lib/binance.ex

@@ -137,21 +137,17 @@ docs
       """
 
       # fx without opts
-      @spec unquote(fx_name)(String.t() | nil, String.t() | nil, unquote_splicing(spec)) ::
+      @spec unquote(fx_name)(unquote_splicing(spec)) ::
               {:ok, any()} | {:error, any()}
 
       # fx with opts
       @spec unquote(fx_name)(
-              String.t() | nil,
-              String.t() | nil,
               unquote_splicing(spec),
               unquote(optional_args)
             ) ::
               {:ok, any()} | {:error, any()}
 
       def unquote(fx_name)(
-            api_key \\ unquote(Application.get_env(:binance, :api_key)),
-            secret_key \\ unquote(Application.get_env(:binance, :secret_key)),
             unquote_splicing(arg_names),
             opts \\ []
           ) do
@@ -160,6 +156,8 @@ docs
         # merge all passed args together, so opts + passed
         all_passed_args = Keyword.merge(binding, opts)
         |> Keyword.drop([:opts, :api_key, :secret_key])
+        api_key = Keyword.get(opts, :api_key) || Application.get_env(:binance, :api_key) || ""
+        secret_key = Keyword.get(opts, :secret_key) || Application.get_env(:binance, :secret_key) || ""
 
         # if the call requires a timestamp, we add it
         adjusted_args =