Add a migration task in the version handler in order to migrate the ETK module from 4.4.6 to 4.5.7 and higher.
Magnolia 4.4.6 shipped ETK 1.4.4
Magnolia 4.5.0 shipped ETK 2.0

If a Magnolia instance is updated from 4.4.6 to 4.5.7, the version handler (DeltaBuilder.update("2.0", "")) will take care of the migration of the module.
If a Magnolia instance was already updated let say from 4.4.6 to 4.5.6 (Version 2.0.6 of the ETK module) and we want now to update to Magnolia 4.5.7, in this case, the version handler's will not run the migration.
Migration already took place during update from 4.4.6 to 4.5.6. and should not run again.
This is exactly what we expected.

Add dependency to the migration module into the module descriptor of ETK.