Multi language support

[overbost]

It is appreciate if the messages and the response will managed by a simple module.
This will allow to easy add languages and edit the error code in one place.
I implemented this features in my API and i will edit this project to allow the multi-languages and the error code manager, but i hope the project will update with this features.

[overbost]

This is my implementation (link expire in 30 days)
https://ufile.io/abwr1e38

It check if you pass "lang=en" in URL, then if there is "lang" in identity with flask-jwt-extended, default is "en"
There is "keys" file with the keys returned for specific errors
Strings is moved and managed in language files
This module should be extern to flask-validator because it can be used with other code outside