enable datetime objects in parser

prototypes/t_qt_2.py

@@ -221,7 +221,7 @@ class FlatBaseModel(BaseModel):
 
     def to_db(self) -> dict[str, Any]:
         """Ausgang für die DB: Flach, Listen sind JSON-Strings."""
-        nested = super().model_dump(mode="json")
+        nested = super().model_dump()
         return self.__flatten_dict(nested, serialize_lists=True)
 
     def to_gui(self) -> dict[str, Any]:
@@ -251,7 +251,7 @@ class FlatBaseModel(BaseModel):
                         processed_list.append(item)
 
                 if serialize_lists:
-                    items.append((new_key, json.dumps(processed_list)))
+                    items.append((new_key, json.dumps(processed_list, default=_parse_json)))
                 else:
                     items.append((new_key, processed_list))
             else:
@@ -259,6 +259,15 @@ class FlatBaseModel(BaseModel):
         return dict(items)
 
 
+def _parse_json(value: Any) -> str:
+    if isinstance(value, datetime.date):
+        return value.isoformat()
+    elif isinstance(value, datetime.datetime):
+        return value.isoformat()
+    else:
+        raise TypeError
+
+
 @dc.dataclass(slots=True)
 class CountryList:
     iso_to_country: dict[str, str]