Add ValidateInstance.By(Func<T, bool> isValidDelegate) overload

Yes,
The parameter "c" is IConstraintValidatorContext

Hi, looking at my code, i see that i use many of this validations:

ValidateInstance.By((x, c) => AssertThatAssociationHasMaxTwoSides:cross_mark:).WithMessage("an association can have two sides at most.");
ValidateInstance.By((x, c) => AssertThatBidirectionalAssociationHasConsistentTypes:cross_mark:).WithMessage("the 2 sides of an association must have consistent types.");
ValidateInstance.By((x, c) => AssertThatBidirectionalAssociationHasOneInverseSide:cross_mark:).WithMessage("a bidirectional association must have one inverse side.");
ValidateInstance.By((x, c) => AssertThatNameIsUnique:cross_mark:).WithMessage("Field name must be unique in containing type.");
ValidateInstance.By((x, c) => AssertThatIdIsUnique:cross_mark:).WithMessage("Field id must be unique in containing type.");
ValidateInstance.By((x, c) => AssertThatTypeExists:cross_mark:).WithMessage("referenced Type does not exists.");

So i think that the feature i'm requesting is already there.

Which is the aggregate value ?
In general, where you have invalid values, you have to add messages to the IConstraintValidatorContext