add warning log about incorrectly nested model config

frigate/config/config.py

@@ -560,6 +560,9 @@ class FrigateConfig(FrigateBaseModel):
 
             # users should not set model themselves
             if detector_config.model:
+                logger.warning(
+                    "The model key should be specified at the root level of the config, not under detectors. The nested model key will be ignored."
+                )
                 detector_config.model = None
 
             model_config = self.model.model_dump(exclude_unset=True, warnings="none")