UniqueConstraintViolationError

[grazianodev]

Right now, when a unique constraint violation occurs, Payload surfaces it as a generic ValidationError. The only way to determine that the error is specifically a unique constraint violation is to inspect the error message and check whether it is "Value must be unique".

I think relying on the error message for this is fragile and makes it difficult to handle unique constraint violations reliably. I’d prefer a more specialized UniqueConstraintViolationError that would allow consumers to distinguish these errors programmatically and handle them appropriately.