Fixed phpstan issues

Author: Fa-BRAIK

src/Support/Traits/HasSerializers.php

@@ -82,5 +82,8 @@ public function serializers(): array
         return $this->_serializers ??= $this->resolveSerializers();
     }
 
+    /**
+     * @return list<Serializer>
+     */
     abstract protected function resolveSerializers(): array;
 }

tests/Dummies/Serializers/HasSerializersDummyClass.php

@@ -4,6 +4,7 @@
 
 use Nuxtifyts\PhpDto\Contexts\PropertyContext;
 use Nuxtifyts\PhpDto\Exceptions\UnknownTypeException;
+use Nuxtifyts\PhpDto\Serializers\DateTimeSerializer;
 use Nuxtifyts\PhpDto\Serializers\Serializer;
 use Nuxtifyts\PhpDto\Support\Traits\HasSerializers;
 
@@ -22,11 +23,13 @@ public static function testGetSerializersFromPropertyContext(PropertyContext $pr
     }
 
     /**
-     * @return list<Serializer>
+     * @return list<class-string<Serializer>>
      */
     protected static function serializersList(): array
     {
-        return [];
+        return [
+            DateTimeSerializer::class
+        ];
     }
 
     /**