validators\Validator $message

The user-defined error message. It may contain the following placeholders which will be replaced accordingly by the validator:

• {attribute}: the label of the attribute being validated
• {value}: the value of the attribute being validated

Note that some validators may introduce other properties for error messages used when specific validation conditions are not met. Please refer to individual class API documentation for details about these properties. By convention, this property represents the primary error message used when the most important validation condition is not met.