Mapping Errors to Status Codes

To get the status code that matches an error, call the StatusFor function:

status := httpapi.StatusFor(err)

It checks the categories in this order:

Error	Status code
`nil`	`200 OK`
`httpapi.ErrUnauthorized`	`401 Unauthorized`
`httpapi.ErrForbidden`	`403 Forbidden`
`httpapi.ErrTooLarge`	`413 Request Entity Too Large`
`httpapi.ErrUnsupportedMediaType`	`415 Unsupported Media Type`
`httpapi.ErrMalformed`	`400 Bad Request`
`httpapi.ErrNotFound`, `query.ErrNoItems`	`404 Not Found`
`architecturekit.ErrDomain`	`422 Unprocessable Entity`
`architecturekit.ErrConflict`	`409 Conflict`
`architecturekit.ErrTransient`	`503 Service Unavailable`
any other error	`500 Internal Server Error`