We need a way to inject serializers and deserializers for new types of entities. This can be done using a DispatchingSerializer. There are some things that need to be done though:

• We want some callbacks to create serializers for a single type of entity (T76021).
• Therefore, we should create public methods to create serializers and deserializers for Item and Property individually. A new DispatchableDeserializer can then be created in a place where all supported entity types are known.
• The Wikibase Internal Serialization component then also needs some adjustments.