Revamp auth module

[manniL]

The current state of the auth-module isn't the best. It is widely used so we should definitely give it some more love :heart:

• [ ] Revamp docs
• [ ] Clean up issues and PRs
• [ ] Add more examples
• [ ] Add better tests

Authentication is by far not the easiest topic but I'm certain we will get this! :raised_hands:

[atinux]

Currently done with the V5, closing it so people can participate there :blush: