Django-idp-user

Added `boto3` as a dependency.

* Replaced `idp_user_id` of the `User` model with an AutoField `id`
* Used `username` as the identifier of the User, both in User creation and user retrieval.
* Simplified authentication logic, removing check with User id.

**Full Changelog**: https://github.com/CardoAI/django-idp-user/compare/v1.1.5...v1.1.6

**Full Changelog**: https://github.com/CardoAI/django-idp-user/compare/v1.1.2...v1.1.4

**Full Changelog**: https://github.com/CardoAI/django-idp-user/compare/v1.1.1...v1.1.2