We need to implement Hibernate's entity class hierarchy persistence and retrieval.

Refer to relevant chapter in Hibernate's user guide for further details: https://docs.jboss.org/hibernate/orm/6.6/userguide/html_single/Hibernate_User_Guide.html#entity-inheritance

We might well create sub-tasks for each of the mapping strategies:

• single table
• joined table
• each class with its own table

The polymorphism should also be supported for @Embeddable @Struct.

The "joined table" strategy requires the completion of https://jira.mongodb.org/browse/HIBERNATE-65