Add support to specify attribute on unique rule

Author: thecodeholic

core/Model.php

@@ -65,10 +65,11 @@ public function validate()
                 }
                 if ($ruleName === self::RULE_UNIQUE) {
                     $className = $rule['class'];
+                    $uniqueAttr = $rule['attribute'] ?? $attribute;
                     $tableName = $className::tableName();
                     $db = Application::$app->db;
-                    $statement = $db->prepare("SELECT * FROM $tableName WHERE $attribute = :$attribute");
-                    $statement->bindValue(":$attribute", $value);
+                    $statement = $db->prepare("SELECT * FROM $tableName WHERE $uniqueAttr = :$uniqueAttr");
+                    $statement->bindValue(":$uniqueAttr", $value);
                     $statement->execute();
                     $record = $statement->fetchObject();
                     if ($record) {