If an Access Denied error occurs, we should
return 403 Forbidden instead of 400 Bad Request.
Gateway Timeout error we also need to process
and return the 504 Gateway Timeout code.
Signed-off-by: Roman Loginov <r.loginov@yadro.com>
HTTP Gateway expects io.Reader to work with
payload, however `WithPayload` flag reads whole
payload into header object.
Signed-off-by: Alex Vanin <a.vanin@yadro.com>
