diff abstract method
Creates a new instance of the entity with updated values.
Computes the difference between the current entity state and an
oldVersion of the entity.
Implementation
// copyWith is not defined in the mixin to allow flexible implementations
/// Computes the **difference** between the current entity state and an
/// [oldVersion] of the entity.
@override
Map<String, dynamic>? diff(covariant DatumEntityInterface oldVersion);