OAuth and access tokens - [PIP-25]

[matyix]

This work is intended to introduce GitHub OAuth authentication and JWT based authentication to the project. Authentication is done at http://127.0.0.1:9090/auth/login address. Token generation is possible after this at http://127.0.0.1:9090/api/v1/token right now in the browser only.

Requirements:

• Registering a GitHub OAuth application and provide the ClientID and ClientSecret in the config.toml file (callback is http://127.0.0.1:9090/auth/github/callback)

Some leftovers:

• JWT Token signing is symmetric (HS256) right now, it should be asymmetric (RS256) for increased security
• Valid tokens are stored in-memory right now, but these tokens should be stored in some kind of fast persistent storage, behind the TokenStore interface.