Use global namespace+minor fixes

Models/Promotion.php

@@ -133,7 +133,7 @@ class Promotion
 
     public function countTasks() : int
     {
-        return count($this->tasks);
+        return \count($this->tasks);
     }
 
     public function getStart() : \DateTime

Models/PromotionMapper.php

@@ -57,6 +57,11 @@ final class PromotionMapper extends DataMapperAbstract
      *
      * @var array<string, array<string, null|string>>
      * @since 1.0.0
+     */    /**
+     * Has many relation.
+     *
+     * @var array<string, array<string, string>>
+     * @since 1.0.0
      */
     protected static $hasMany = [
         'tasks' => [