anchor.diff:        {_, <<"authorization_code">>} ->
           authorization_code_flow_stage2(Req, State);
         {_, <<"password">>} ->
  -        resource_owner_password_credentials_flow(Req, State);
  +        password_credentials_flow(Req, State);
         {_, <<"client_credentials">>} ->
           client_credentials_flow(Req, State);
         _ ->
  
positive.code: %%------------------------------------------------------------------------------
  %% Authorization Response
  %%------------------------------------------------------------------------------
  
  authorization_decision(Req, State = #state{response_type = <<"code">>,
      client_id = ClientId, redirect_uri = RedirectUri,
  
negative.code: %%
  %% Request access token for a resource owner.
  %%
  password_credentials_flow(Req, State = #state{
      data = Data, options = Opts
    }) ->
    % @todo ensure scheme is https
  