Add an IsRequired property to PropertyShape and ParameterShape attributes.

[eiriktsarpalis]

Users should be able to control the requiredness of individual properties or constructor parameters using attribute annotations. Today this can only be changed influenced using either the required keyword or by marking a constructor parameter as optional.

[AArnott]

Today this can only be changed influenced using either the required keyword or by marking a constructor parameter as optional.

This seems sufficient to me. Are there cases where we want to diverge from these indicators?

[eiriktsarpalis]

I've received a lot of feedback from STJ users needing to decouple the contract of the type from the contract of serialization.

[AArnott]

So the idea is a hard rejection of data during deserialization if it omits a property that is marked as required this attribute?

[eiriktsarpalis]

Correct, although this still needs to be implemented at the individual converter layer.