LazyId should be splitted into null and non-null variants

[a-vezzoli-02]

Is your feature request related to a problem? Please describe.
Always have to check if the value of a LazyId is null or not makes the code "heavy". Also there are cases where a LazyId cannot have a null value (for example when a foreign key has a NON NULL)

Describe the solution you'd like
Splitting the LazyId class into different classes:

• a generic one (the current LazyId)
• a null one
• a non-null one

Note that LazyId would then become a sealed class and the variants would be subclasses.

Describe alternatives you've considered
Probably also splitting the non-null variant into:

• a non-null lazy one
• a non-null defined one

could be useful

Additional context
No.

[a-vezzoli-02]

This is not fully doable. What can be done is to make LazyId always return non-null values. In this scenario, LazyId itself would be null.
This way the "null-check" will be necessary only if the value of the Table could be null, thus reducing the needing for "null-checking" even if the value could never be null.