Automate Auth0 custom actions setup

[snorremd]

Currently the Ajanottaja API requires you to set up some Auth0 flows and custom actions manually. This process involves creating two custom actions for post registration and pre-login flow, assigning them to the flows, and deploying them. If the scripts need to change in a breaking way the scripts need to be manually updated.

Instead the Ajanottaja API should be able to bootstrap the Auth0 setup itself using the Auth0 Management API. It can create the script (versions), make sure they are assigned to the flows, etc. When new versions are enabled the API can deploy them. This will help those that want to host Ajanottaja themselves without having to do lots of manual work.

[snorremd]

A MVP implementation was completed with 5603962. Still needs some fine tuning. We likely don't want to run this on every Ajanottaja startup.