- DBAL 4.5 (required by DoctrineBundle 3, needed for Symfony 8).
- array/object types (removed from DBAL 4): App\Doctrine\Type\Serialized
  ArrayType/ObjectType, same storage as DBAL 3 (roles, Flux::$data, Gedmo
  log entries, Payum tokens): no data migration.
- Migration: the DC2Type column comments are removed (162 columns, comment
  only: types, nullability and defaults checked unchanged; down() restores
  the original schema exactly, tested).
- Explicit decimal precision (10, the former DBAL default) and string length
  (classification context id), now required.
- Old migrations: platform check without getName() (removed), and
  IdToUuidMigration getLocalColumns(): a fresh install (all migrations on an
  empty database) works and gives the mapped schema.