class UniqueFieldConstraint

class UniqueFieldConstraint extends SymfonyConstraint {
    public $message = 'A @entity_type with @field_name %value already exists.';
    
    /**
     * This constraint is case-insensitive by default.
     *
     * For example "FOO" and "foo" would be considered as equivalent, and
     * validation of the constraint would fail.
     *
     * @var bool
     */
    public $caseSensitive = FALSE;
    
    /**
     * Returns the name of the class that validates this constraint.
     *
     * @return string
     */
    public function validatedBy() {
        return '\\Drupal\\Core\\Validation\\Plugin\\Validation\\Constraint\\UniqueFieldValueValidator';
    }

}