Update dependencies

Improvements:

• Update dependencies to support Django 2.2
• Conform with Django convention adding trailing slash to all endpoints

Social registration fields mappping

Features:

• Ability to specify how the social user payload fields map to User model fields
• Ability to override the default behavior of computing the USERNAME_FIELD value on social user registration

Bug fixes:

• Social registration failed for custom User models without the username field

Chore:

• Improve tests by splitting them into default and custom user tests

Improve social view error responses

Improvements:

• Social auth views returned a generic "Bad token" response on access token response verification. Now they are extensible and return the actual error for Google view.

Endpoints restructure and social improvements

Improvements:

• Social endpoints return the user information on the response
• Social endpoints respect user-defined UserSerializer and Register Fields
• Authentication endpoints restructuring to a single AuthView class with base protocol

Fix register fields requirement

Bug fixes:

• Fix dependency on both username and email on default UserSerializer

Fix missing dependency

Bug fixes:

• Add missing dependency on setup.py

CKL Auth basic features

Features:

• Login endpoint
• Register endpoint
• Reset password endpoint
• Google log in/sign up
• Facebook log in/sign up