Use global namespace+minor fixes

Models/QAAnswer.php

@@ -103,6 +103,9 @@ class QAAnswer implements \JsonSerializable
         return $this->createdAt;
     }
 
+    /**
+     * {@inheritdoc}
+     */
     public function jsonSerialize() : array
     {
         return [];

Models/QACategory.php

@@ -59,6 +59,9 @@ class QACategory implements \JsonSerializable
         $this->parent = $parent;
     }
 
+    /**
+     * {@inheritdoc}
+     */
     public function jsonSerialize() : array
     {
         return [];

Models/QAQuestion.php

@@ -161,6 +161,9 @@ class QAQuestion implements \JsonSerializable
         $this->answers[] = $answer;
     }
 
+    /**
+     * {@inheritdoc}
+     */
     public function jsonSerialize() : array
     {
         return [];

Models/QAQuestionMapper.php

@@ -50,6 +50,11 @@ final class QAQuestionMapper 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 = [
         'answers' => [