Currently we only migrate the client and SSSSCache but this leads to the
problem that we are no longer self signed after the migration.
We need to migrate all device keys too.
This also abstracts the migration code in a method. init() is too large already...
The hive database now implements the whole API except for storing files which
should be better done by the flutter_cache_manager package inside of the
flutter app. All tests already run with Hive now but the Moor database is still
tested too. We needed to change some wait jobs in the tests because the Hive
database is not 100% in memory for the tests like Moor.
For now both database implementations are equal and the developer can pick
which one to use but we plan to get rid of Moor in the future.
Christian Pauly