Migrate to CBOR instead of BSON
Currently, the app uses binary JSON to store items in the cache. However, the appropriate methods in the
QJSONDocument class have been deprecated. Most probably, they won't be supported any longer with Qt 6. Consequentially, we should add some code to migrate to the new CBOR format instead. We either:
- Could migrate the cache upon app start. This might take some time in which the cache cannot be used otherwise.
- It hence could be easier to just drop the cache completely and re-initialize it once. This could also be used for further restructuring if desired.