Analyze "user upgrade" functionality and consider whether it can be removed

The /update endpoint is mapped to a basic UI and a front-end controller calling /rest/accounts/{username:.+}/updateTask.

The latter in the AccountController invokes the functionalities in the DefaultUpgradeService, which at this time, seem to only provide an abstraction framework for some user account upgrade tasks.

I haven't found yet whether there is any automatic/conditional redirection of a user's request to that endpoint.

It also looks like there is some confusion in between upgrading a user account (which would suggest some role changes to me) and the tasks currently implemented, which suggest updates to model content (Vortolang etc. ) - i.e. not the user itself.

Generally speaking, it seems this was thought of as a "glue" to allow automatic migration of older data formats.

The code is pretty old (mostly 2018 - early 2019), and could use an in-depth review on whether we still need it at all.