ErrorResponse takes a response status code and arbitrary data and writes a json response to the client in depends on Header Accept and APP_ENV environment variable(has two possible values: dev and prod) - APP_ENV=dev responds debug info level of error - APP_ENV=prod responds just message about error [DEFAULT].

SuccessResponse takes a response status code and arbitrary data and writes a json response to the client in depends on Header Accept.

ErrResponse is the type used for sending JSON around.

Response is the type used for sending JSON around.