Added clear method.

core/lib/Thelia/Coupon/Type/CouponAbstract.php

@@ -499,4 +499,11 @@ abstract class CouponAbstract implements CouponInterface
 
         return $effects;
     }
+
+    /**
+     * @inheritdoc
+     */
+    public function clear() {
+        // Does nothing. Override this function as needed.
+    }
 }

core/lib/Thelia/Coupon/Type/CouponInterface.php

@@ -239,4 +239,9 @@ interface CouponInterface
      */
     public function getEffects($data);
 
+    /**
+     * Clear all the data the coupon may have stored, called after an order is completed.
+     */
+    public function clear();
+
 }