[TYPE 3] [Allow to override constants]  #1186

Summary

Create a configuration file to centralize all constant in a single place, allowing users to override values as needed (Monkey patching)

Description

There is a constant FILESIZE_LIMIT in the datasources_endpoint.py file that is hardcoded to chunk files after 64 MB.

Security policies implemented in a firewall on top of an application could have constrains about the max size of body request or max file upload that could differ in case to case and requires file to be chunked in smaller pieces.