Added Writeonly converter. (features & fixes)

Add some typing information, or make it consistent. Add more docstrings. Fix using Skip in switch converter.

field.py

@@ -187,7 +187,7 @@
         message_value: Any,
         instance: models.BaseModel,
         value_present: bool = True,
-    ) -> dict:
+    ) -> dict | SkipType:
         message = super().message_to_odoo(
             odoo_env, phase, message_value, instance, value_present
         )
@@ -191,7 +191,7 @@
         message = super().message_to_odoo(
             odoo_env, phase, message_value, instance, value_present
         )
-        if self.field_name in message:
+        if not isinstance(message, SkipType) and self.field_name in message:
             self._lazy_dicts(instance)
             message[self.field_name] = self._lazy_dict_message_to_odoo.get(
                 message[self.field_name]