function enumerable(rule, value, source, errors, options) {
  rule[ENUM] = Array.isArray(rule[ENUM]) ? rule[ENUM] : [];
  if (rule[ENUM].indexOf(value) === -1) {
    errors.push(__WEBPACK_IMPORTED_MODULE_0__util__["e" /* format */](options.messages[ENUM], rule.fullField, rule[ENUM].join(', ')));
  }
}
Rule for validating a value exists in an enumerable list.

 @param rule The validation rule.
 @param value The value of the field on the source object.
 @param source The source object being validated.
 @param errors An array of errors that this rule may add
 validation errors to.
 @param options The validation options.
 @param options.messages The validation messages.