This is just to document some general changes we should look into and probably apply to the codebase for Picard 3 so we don't forget about this.

• Check code for deprecated methods and remove them
• Turn the Item.can_{} and Item.is_ methods into properties
• Get rid of QObject.tagger. Explicitly pass tagger instance around, or where this is not feasible use QCoreApplication.instance()
• Consider wrapping QCoreApplication.instance() into an own function (e.g. Tagger.instance() static method)
• Same for QObject.log and QObject.config
• Check for workarounds for specific issues with dependency, validate if the workarounds are still needed with the new minimum versions of requirements
• Rename variables / functions / options related to non album tracks to standalone recordings for consistency