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Это по сути тоже сужает действие, но позволяет применить к кастомным Constraint'ам https://docs.jboss.org/hibernate/validator/4.1/ref... https://beanvalidation.org/1.1/spec/
Payloads are typically used by validation clients to associate some metadata information with a given constraint declaration. Payloads are typically non-portable. Describing payloads as interface extensions as opposed to a string-based approach allows an easier and more type-safe approach.