Fail will send the status code, write the error's reason and return the HTTPError for further use, i.e logging, see `InternalServerError`.

FailJSON will send to the client the error data as JSON.

InternalServerError logs to the server's terminal and dispatches to the client the 500 Internal Server Error.

InternalServerErrorJSON acts exactly like `InternalServerError` but instead it sends the data as JSON.

LogFailure will print out the failure to the "logger".

RuntimeCallerStack returns the app's `file:line` stacktrace to give more information about an error cause.

UnauthorizedJSON sends JSON format of StatusUnauthorized(401) HTTPError value.

HTTPError describes an HTTP error.