reason property
The reason of the field-level error. This is a constant value that
identifies the proximate cause of the field-level error. It should
uniquely identify the type of the FieldViolation within the scope of the
google.rpc.ErrorInfo.domain. This should be at most 63
characters and match a regular expression of [A-Z][A-Z0-9_]+[A-Z0-9],
which represents UPPER_SNAKE_CASE.
Implementation
final String reason;