add doc about filterHandler

docs/entities/query.md

@@ -141,6 +141,32 @@ class MyEntityRepositoryQuery extends RepositoryQuery
 }
 ```
 
+You can also force `filterHandler` te be used for specific filter field:
+
+```php-inline
+// ...
+
+class MyEntityRepositoryQuery extends RepositoryQuery
+{
+    public function __construct(Repository $repository, PaginatorInterface $paginator)
+    {
+        // ...
+
+        $this->addForcedFilterHandler('foo');
+    }
+
+    public function filterHandler(string $name, $value): self
+    {
+        // ...
+
+        if ($name === 'foo) {
+            // ...
+        }
+    }
+
+}
+
+```
 
 ## Pager