Role management fixes

There are still some issues left that we decided to move to another MR after MVP version is merged:

• Use Hydra to fetch the apps list (we will do that later while developing apps)
• Fix app links on dashboard < this is only broken on localhost
• Protect dashboard backend with permission layer (we will use decorators for that)
  • dashboard-backend!76 (merged)
• There will be three roles (No app access, User access, Admin access). All of these should have existing roles & role IDs, but we might want to default null (or no role) to "no app access" for now (I believe the original wireframes also included the users to be able to set default app access per app, but if we implement that, I say we do it somewhere in the future). (see also #40 (closed))
  • dashboard-backend!75 (merged)
  • !31 (merged)
• If the user rights are changed we need to update the frontend on refresh
  • Not sure about the status of this one, but we'll open a new issue if this is still a problem.
• Nextcloud is 1 word, so next-cloud in the app list (used in const initialAppRoles) is incorrect. This might also lead to problems down the road, when setting permissions for nextcloud. next-cloud should be replaced by nextcloud everywhere. NextCloud should be replaced by Nextcloud.
  • fixed in !31 (merged)