[Delayed] Support GitHub - because Intellij bundled plugin supports comment feature

[nhat-phan]

Documentation: https://developer.github.com/v3/ Github client: https://github.com/github-api/github-api

Acceptance Criteria:

• [ ] Can config an connection to GitHub
• [ ] Can see the list of pull requests assigned to logged in user/wait for logged in user to review
• [ ] Can filter the pull requests by status (merged/opened/closed)
• [ ] Can see commits
• [ ] Can see comments
• [ ] Can leave a comment in a specific position
• [ ] Can delete a comment

Nice to have:

• [ ] Filter by assigner/reviewer
• [ ] Pipeline status
• [ ] Can resolve a comment

Tasks:

• [x] Configuration page
• [x] Implement User Api
• [x] Implement Project Api - for github it’s Repository api
• [ ] Implement Merge Request Api - for github it’s Pull Request
• [ ] Implement Comment Api
• [ ] Manual testing

Notes/difficulties/questions:

1. How to get members of the repository?
2. How to get pipeline status of the pull request? Required information:

• Latest pipeline status: running/passed/failed
• Web url of latest pipeline

3. Should the throttle limit be displayed somewhere? ~~if yes how to log the request by time effectively?~~ -> use https://api.github.com/rate_limit
4. Is there any self-signed certificate concern for custom GitHub server?

[nhat-phan]

Intellij supports a bundled Github plugin which have a comment functionality since 2020.1 EAP version. So I'll focus on improving the plugin functionality before porting to Github.