multiple enhancements to model manager REACT API

1. add a /sync route for synchronizing the in-memory model lists to
   models.yaml, the models directory, and the autoimport directories.

2. add optional destination_directories to convert_model and merge_model
   operations.

3. add /ckpt_confs route for retrieving known legacy checkpoint configuration
   files.

4. add /search route for finding all models in a directory located in the server
   filesystem

invokeai/app/services/model_manager_service.py

@@ -167,6 +167,15 @@ class ModelManagerServiceBase(ABC):
         """
         pass
 
+    @abstractmethod
+    def list_checkpoint_configs(
+        self
+    )->List[Path]:
+        """
+        List the checkpoint config paths from ROOT/configs/stable-diffusion.
+        """
+        pass
+
     @abstractmethod
     def convert_model(
         self,
@@ -220,6 +229,7 @@ class ModelManagerServiceBase(ABC):
             alpha: Optional[float] = 0.5,
             interp: Optional[MergeInterpolationMethod] = None,
             force: Optional[bool] = False,
+            merge_dest_directory: Optional[Path] = None
     ) -> AddModelResult:
         """
         Merge two to three diffusrs pipeline models and save as a new model.
@@ -228,6 +238,7 @@ class ModelManagerServiceBase(ABC):
         :param merged_model_name: Name of destination merged model
         :param alpha: Alpha strength to apply to 2d and 3d model
         :param interp: Interpolation method. None (default) 
+        :param merge_dest_directory: Save the merged model to the designated directory (with 'merged_model_name' appended)
         """
         pass
 
@@ -238,6 +249,15 @@ class ModelManagerServiceBase(ABC):
         """
         pass
         
+    @abstractmethod
+    def sync_to_config(self):
+        """
+        Re-read models.yaml, rescan the models directory, and reimport models 
+        in the autoimport directories. Call after making changes outside the
+        model manager API.
+        """
+        pass
+        
     @abstractmethod
     def commit(self, conf_file: Optional[Path] = None) -> None:
         """
@@ -438,16 +458,18 @@ class ModelManagerService(ModelManagerServiceBase):
         """
         Delete the named model from configuration. If delete_files is true,
         then the underlying weight file or diffusers directory will be deleted
-        as well. Call commit() to write to disk.
+        as well.
         """
         self.logger.debug(f'delete model {model_name}')
         self.mgr.del_model(model_name, base_model, model_type)
+        self.mgr.commit()
 
     def convert_model(
         self,
         model_name: str,
         base_model: BaseModelType,
         model_type: Union[ModelType.Main,ModelType.Vae],
+        convert_dest_directory: Optional[Path] = Field(default=None, description="Optional directory location for merged model"),        
     ) -> AddModelResult:
         """
         Convert a checkpoint file into a diffusers folder, deleting the cached
@@ -456,13 +478,14 @@ class ModelManagerService(ModelManagerServiceBase):
         :param model_name: Name of the model to convert
         :param base_model: Base model type
         :param model_type: Type of model ['vae' or 'main']
+        :param convert_dest_directory: Save the converted model to the designated directory (`models/etc/etc` by default)
 
         This will raise a ValueError unless the model is not a checkpoint. It will
         also raise a ValueError in the event that there is a similarly-named diffusers
         directory already in place.
         """
         self.logger.debug(f'convert model {model_name}')        
-        return self.mgr.convert_model(model_name, base_model, model_type)
+        return self.mgr.convert_model(model_name, base_model, model_type, convert_dest_directory)
 
     def commit(self, conf_file: Optional[Path]=None):
         """
@@ -543,6 +566,7 @@ class ModelManagerService(ModelManagerServiceBase):
             alpha: Optional[float] = 0.5,
             interp: Optional[MergeInterpolationMethod] = None,
             force: Optional[bool] = False,
+            merge_dest_directory: Optional[Path] = Field(default=None, description="Optional directory location for merged model"),
     ) -> AddModelResult:
         """
         Merge two to three diffusrs pipeline models and save as a new model.
@@ -551,6 +575,7 @@ class ModelManagerService(ModelManagerServiceBase):
         :param merged_model_name: Name of destination merged model
         :param alpha: Alpha strength to apply to 2d and 3d model
         :param interp: Interpolation method. None (default) 
+        :param merge_dest_directory: Save the merged model to the designated directory (with 'merged_model_name' appended)
         """
         merger = ModelMerger(self.mgr)
         try:
@@ -561,6 +586,7 @@ class ModelManagerService(ModelManagerServiceBase):
                 alpha = alpha,
                 interp = interp,
                 force = force,
+                merge_dest_directory=merge_dest_directory,
             )
         except AssertionError as e:
             raise ValueError(e)
@@ -572,3 +598,20 @@ class ModelManagerService(ModelManagerServiceBase):
         """
         search = FindModels(directory,self.logger)
         return search.list_models()
+
+    def sync_to_config(self):
+        """
+        Re-read models.yaml, rescan the models directory, and reimport models 
+        in the autoimport directories. Call after making changes outside the
+        model manager API.
+        """
+        return self.mgr.sync_to_config()
+
+    def list_checkpoint_configs(self)->List[Path]:
+        """
+        List the checkpoint config paths from ROOT/configs/stable-diffusion.
+        """
+        config = self.mgr.app_config
+        conf_path = config.legacy_conf_path
+        root_path = config.root_path
+        return [(conf_path / x).relative_to(root_path) for x in conf_path.glob('**/*.yaml')]