[FEATURE] Add web login (using github)

[darcyclarke]

Description

User's aren't able to use npm login or any other package manager's web login flow to generate a .npmrc (or similar) file with the corresponding user auth token. This is partly because vsr does not have traditional user credentials yet (ie. basic auth creds like username+password).

Suggestion

• Add new GitHub login/authentication mode
  • Leverage an expanded user profile (ie. [FEATURE] Add expanded user profile scopes #6) with user.github to tie github authentication to a user profile/auth token
  • When active, user tokens with user:auth will be connected to the corresponding user.name & user.github account for the purpose of web login
  • A login for that user.name / user.github account will rotate the token
  • If no existing token exists, it's as if the user does not exist
• Add new logout endpoint
  • A logout will remove the token's uuid but not the token entry itself (as it will be rotated/updated on future logins)

[raashidanwar]

Hi @darcyclarke ,

I would like to work on this. I already worked on login flow npmjs.com at github.