Migrate shared djoser functionality to authentication app.

[Wassaf-Shahzad]

Checklist:

• MIgrate the code from the following issue mitodl/mitxpro#2306
• MIgrate the code from the following issue mitodl/mitxonline#147

Description:

The following issues are shared between multiple repositories and can be fixed by migrating their respective PR's into ol-django.

• mitodl/mitxonline#147
• mitodl/mitxpro#2304
• mitodl/bootcamp-ecommerce#1295
• mitodl/mitxpro#2306

The issues described in mitodl/mitxpro#2306 also exist in MITxOnline.