Added Ccstomr User model, User Admin, User Auth APIs, FB auth

[skfarhad]

Added folder- apps/ for Djagno apps:

• This folder will act as a container for Django apps for facilitating better structure for CI/CD pipelines

  Custom User model

• Created a Custom User model so that we can use phone number/password combo for login instead of default username/password of email/password combo.

  User login/Registration API

• Added User login and registration APIs using custom token generation for registration/login. Also added scope for Google/Firebase authentication
• Added necessary endpoint tests with Django unittest

  User admin Panel

• Overriding the default admin panel for users, added custom sections for in admin panel for user management, password reset and filtering

  Common models

• Added common TSFieldsIndexedand TSFields models so that we can use those to create timestamp indexed models without writing repeated logics

  Common CustomViewSet & Pagination classes

• Added a CustomViewSet class with added functionalities so that we may use it for common CRUD operations with custom logic pushed inside create/update/delete/ methods.
• Also provided a Common Pagination class integrated with CustomViewSet