[iOS] Social Login and Authentication

[marcotuts]

Goal

This project involves adding social authentication options including - Apple, Microsoft, Facebook, and Google to the base open edx application

Slack: #wg-product-mobile
Requirement Definition: Confluence Project Page

### Tasks
- [ ] https://github.com/openedx/openedx-app-ios/issues/113
- [ ] https://github.com/openedx/openedx-app-ios/issues/114
- [ ] Confluence Project Page ready for review
- [ ] https://github.com/openedx/openedx-app-ios/issues/159

[Kelketek]

Calling attention to #65 (comment) , which is at least a partial solution to this problem, and which if provided additional resources could be completed.