This PR moves all authentication, authorisation and login sections to Sprout.
Concrete login details are moved to Runtime view (they were mostly there already anyway).
More general discussions about our authentication/authorisation strategies are moved to the Security page that I made. I'm happy to move them somewhere else though!
I left most of the original text intact, only changing it to make it more consistent and flow better.
Description
Related Issues
Goes hand in hand with https://github.com/seedcase-project/design/pull/107
Closes https://github.com/seedcase-project/design/issues/86
Reviewer Focus
This PR only needs a quick review.
Checklist
For general documentation: