feat(deck): add duedate validation to CardServiceValidator

- Added date validation rule for duedate field

Signed-off-by: bahman <bja@adlas.at>

Author: bahman

lib/Validators/CardServiceValidator.php

@@ -21,6 +21,7 @@ public function rules() {
 			'type' => ['not_empty', 'not_null', 'not_false', 'max:64'],
 			'order' => ['numeric'],
 			'owner' => ['not_empty', 'not_null', 'not_false', 'max:64'],
+			'duedate' => ['date'],
 		];
 	}
 }