Developers do not have a mechanism to handle the situation where a Realm file version is required when upgrading Realm to a newer version.

We should provide a mechanism to graceful handle this situation, allowing them to notify their users that an update is going to start, its progress, and when it has completed.

This requirement comes from a Real scenario where a user reports that a Realm file upgrade takes up to 10 minutes on his app, with no way to report such status to the user.

See: https://github.com/realm/realm-java/issues/7426