Allow to change output structor

[expressjs]

Allow to change output structor

[dougwilson]

Why does the structure matter for development? Don't you want to know what the error is when developing?

[wxs77577]

I wanna use it in production mode, if any where throw an error, it sends an json like {statusCode: 422, message: 'Username is required.'}.

[dougwilson]

This module has no production mode. The description of this module is the following:

Development-only error handler middleware.

This middleware is only intended to be used in a development environment, as the full error stack traces and internal details of any object passed to this module will be sent back to the client when an error occurs.