The COLLECTION_PER_CLASS inheritance type has been deprecated with no replacement. It persisted one
collection per class, which is already the default behavior: every document class is mapped to its own
collection. The strategy provided no additional behavior and could not guarantee _id uniqueness across
the distinct collections of a hierarchy.
Remove the InheritanceType attribute/annotation (or the inheritance-type XML attribute) from the
affected classes. Each class remains mapped to its own collection.
#[ODM\Document]
-#[ODM\InheritanceType('COLLECTION_PER_CLASS')]
class Section {}This effectively deprecates ClassMetadata::isInheritanceTypeCollectionPerClass() and
ClassMetadata::INHERITANCE_TYPE_COLLECTION_PER_CLASS.