Enable extensions (loader)

[barneydobson]

Implement this separately

Original implementation: wsimod/orchestration/model.py

@dalonsoa suggests:

• List of filepaths under extensions entry in the config file.

for extension_file in config.get('extensions',[]):
   # use the import module (see swmmanywhere)`

Nodes

• Check that the node register function updates the model.nodes_type information.
• By importing a node module, it should now be available via the register

Decorators

• Ignore ExtensionHandler from Extensions: decorators #97 , decorators now stored in extensions_register, which makes extensions available to the model.
• A custom decorator will call register_node_method, on import, which will add it to the extensions_register.
• extensions_register will need to be iterated over after the nodes have been instantiated inside model.load, as demonstrated below.

extensions_register = {
    'node_name' : 
      {
         'method' : method,
      }
}

def apply_decorators(model):
   for node_name, decorator in extensions_register.items():
      if 'sub_object' in decorator:
         setattr(getattr(model.nodes[node_name], decorator['sub_object']), method_name, method)
         continue   
      setattr(model.nodes[node_name], method_name, method)

Sequence

1. Enter model.load
2. Instantiate extensions_register
3. Import extensions
4. Instantiate nodes
5. Apply decorators

To do list

Within #97 - @dalonsoa

• Create extensions_register
• Create register_node_method (optional arg for sub_object).
• Add apply_decorators
• Tests (make tests that can be used in docs)

Within this PR - @dalonsoa

• Implement sequence above
• Tests (make tests that can be used in docs)

Close #54 , make a new PR - @liuly12

• Keep the custom orchestration stuff, bin else

Documentation (new issue)

• Overview of all new functionality (overrides, subclassing, decorators). - @dalonsoa
• Enable decoration of handlers (easy to code - a distinct decorator, e.g., register_node_handler) - us to revisit
• update documentation for 'customise interactions' and 'river reservoir'. @barneydobson
• Take down old documentation on customisation ('customise a node').
• Release here! @dalonsoa
• Longer term issue to update customise a node.