Expose and set configuration to allow OCW to make API calls to Open using an existing session

[rhysyngsun]

The allow OCW to make API calls, we are planning to allow it to utilize an existing Django HTTP session for authentication because OCW has neither a server backend nor a thick client app. To accomodate this, we need to make allowances in several configurations - some are already exposed as environment variables, but some are not:

• Add an environment variable in settings.py for social auth's SOCIAL_AUTH_ALLOWED_REDIRECT_HOSTS
  • See: https://python-social-auth.readthedocs.io/en/latest/configuration/settings.html#processing-requests-and-redirects
• Add the OCW hostname/origin to:
  • SOCIAL_AUTH_ALLOWED_REDIRECT_HOSTS (should be hostname only)
  • CORS_ALLOWED_ORIGINS (protocol + domain)