add doc about filterHandler

docs/entities/query.md

@@ -114,6 +114,34 @@ $entities = $query->create()
     ->find();
 ```
 
+In the context of a CRUD, filters are applied using [the method `useFilters`](https://gitnet.fr/murph/murph-core/src/branch/master/src/core/Repository/RepositoryQuery.php#L78-L99).  
+Integers, strings and booleans are automatically processed. Other types are passed to [the method `filterHandler`](https://gitnet.fr/murph/murph-core/src/branch/master/src/core/Repository/RepositoryQuery.php#L122-L124).
+
+You have to override it to manage them, example:
+
+```php-inline
+// ...
+
+use App\Entity\Something;
+
+class MyEntityRepositoryQuery extends RepositoryQuery
+{
+	// ...
+
+    public function filterHandler(string $name, $value): self
+    {
+        if ($name === 'something' && $value instanceof Something) {
+            $this
+                ->join('something', 's')
+                ->andWhere('s.id = :something')
+                ->setParameter('something', $value->getId())
+            ;
+        }
+    }
+}
+```
+
+
 ## Pager
 
 You can paginate entities (`Knp\Component\Pager\Pagination\PaginationInterface`):