Automated upgrade of database on start of app

[andrew-codes]

Some major version changes require changes to the database's schema. Historically, the recommendation is to drop the entire database and perform a Playnite Web sync after starting the upgraded application. This only works because there is currently no data in the database that is not from a sync. However, there are upcoming features that will require non-synced data to be stored, in which case we would not want to drop the database due to schema changes. For this reason, we want to enable the ability to automatically migrate an existing database and its data to a new release's schema.

When starting the application, it should compare its version to the current database schema version (will require tracking the application version in persistent storage). If the versions are different, then it should perform an upgrade script (if defined) to go from the current version to the next major version. This should be done for each major version in between the database schema's version and the running application's version. This should be successfully completed before starting the rest of the application.

• Migration should occur when starting the application. It should be successfully completed prior to the running of the application (web server, etc.).
• Unsuccessful migrations should prevent the application from starting
• A migration is defined for a given major release. A major release may or may not have a migration associated to it.
• If there are multiple migrations available, then they are performed sequentially in ascending order.