[VNG-Realisatie#215] add DurationFieldExtension

vng_api_common/extensions/fields/duration.py

@@ -0,0 +1,19 @@
+from drf_spectacular.extensions import OpenApiSerializerFieldExtension
+
+
+class DurationFieldExtension(OpenApiSerializerFieldExtension):
+    target_class = "rest_framework.fields.DurationField"
+    match_subclasses = True
+
+    def map_serializer_field(self, auto_schema, direction):
+        default_schema = auto_schema._map_serializer_field(
+            self.target, direction, bypass_extensions=True
+        )
+
+        schema = {
+            **default_schema,
+            "format": "duration",
+        }
+
+        verbose_name = getattr(self.target, "label", None)
+        return {**schema, "title": verbose_name} if verbose_name else schema