Refactor / Changes to Make Skygear Auth Independent

[chpapa]

Description

We need to review current design and see if we can / how shall we make Skygear Auth more independent, at least the following ways:

1. A separate Github Repo and README.md to explain the concept (For easier Developer's understanding / HN submissions)
2. Simple Self-Deployment (Ideally a simple Docker image)
3. Usable with 3rd parties backend easily, probably in two ways:
   • Via OIDC/JWT: e.g. a PHP developer can just start the Docker image, use the Auth UI, and got the tokens to create a session in Laravel PHP
   • Via k8s gateway integration: e.g. Skygear's own gateway, could support others like Kong / Trafik gateway in future

Open Questions

Put a list of open questions here before a complete design / specification is decided

Related Issues

• Server Issues
• Client Issues
• Guides Issues