Akonadi master now has a new thing called "generation" (Akonadi::ServerManager::generation()), which can be used to detect when Akonadi database is deleted and created again.

All applications should now store the generation number in their config files and check on start whether it matches the current Akonadi generation number and invalidate their configuration options which refer to Akonadi IDs (collection IDs or tag IDs etc.) if the generation has changed.