When using update_interval and call_interval, the limit computed for the first user is used for all other users (which, when the first user is admin and has no feeds, breaks the update).
This is a major change for the next release of Miniflux.
- There is now only one database that can supports multiple users
- There is no automated schema migration for this release
- A migration procedure is available in the ChangeLog file
Check if a requested database can be selected. Error out if not.
This prevents automatic fallbacks to the default database.
Remove the authorized information from the session if a new database
gets selected.
Factor out logout function to reuse existing code.
