We currently always return a non-null instance for complex properties, including when all their columns are null. We may need to add an option to opt into optional complex types, where if all properties are null, null is returned instead.

See #9005 for the same thing with owned entity types.

• Model building and validation
• Relational and compiled model support
• Migrations support
• Change tracking support
• Add complex type discriminators that can be used as a marker if all other properties are optional
• Query support
• ExecuteUpdate support