What has changed with this PR?

The PR addresses a few aspects.

1. Performance.
   Loading polls was rather slow with a big amount of polls, since there were a lot of database requests, mainly for permission checks and when dealing with the acl.
   The new approach loads all necessary informations for the permission checks from the database via subqueries and joins. This way, permissions can be checked directly inside the poll.
   As a result the old usage of the Acl has been changed and the new Acl carries not any poll informations, but the user information based on the UserSession and the app permissions.
2. Move permission checks to the service layer, so the controllers are free from the permission checks.
3. Further steps to prepare creating polls without the necessity to be logged in.
4. Preparation of the upcomming vue3 migration
   In the result the structure of the API has changed for a better segmentation. The most important change is, that all changable properties are collected inside the configuration node of the json structure.

The following vue3 migration will be done in two steps:
1. Migrating from vuex to pinia and typescript
2. The final migration to vue3 with the options API including updating the stores
3. Further rolling by-the-way migration of the options API to the composition API

@Bagoult FYI, since you are working with the API.

The structure layout is rather final, but may still get some updates in detail. Also the user objects will still receive some optimizations. I plan to get this API (v1.0) finalized.

To dos:

• Remove loading app settings from publicy accessing users
• Fix relevant listing
• Update user objects