anchor.diff:  %%
   %% content_types_accepted SHOULD return a different list
   %% for each HTTP method.
  -accept_resource(Req, State, OnTrue) ->
  +accept_resource(Req, State) ->
   	case call(Req, State, content_types_accepted) of
   		no_call ->
   			respond(Req, State, 415);
  
positive.code: 			{error, 500, Req};
  		{halt, Req2, HandlerState2} ->
  			terminate(Req2, State#state{handler_state=HandlerState2});
  		{true, Req2, HandlerState2} ->
  			State2 = State#state{handler_state=HandlerState2},
  			next(Req2, State2, OnTrue);
  		{false, Req2, HandlerState2} ->
  			State2 = State#state{handler_state=HandlerState2},
  			respond(Req2, State2, 422);
  
negative.code: 			State2 = State#state{handler_state=HandlerState2},
  			Req3 = cowboy_req:set_resp_header(
  				<<"location">>, ResURL, Req2),
  			if
  				Exists -> respond(Req3, State2, 303);
  				true -> respond(Req3, State2, 201)
  			end
  	end.
  
  %% If the resource is new and has been created at another location
  %% we send a 201. Otherwise we continue as normal.
  maybe_created(Req, State) ->
  	case cowboy_req:has_resp_header(<<"location">>, Req) of
  		true -> respond(Req, State, 201);
  		false -> has_resp_body(Req, State)
  