Creating a custom matter_idl generator

The matter_idl tool can be used to generate arbitrary code based on the Matter data model schemas. To create a custom generator that lives outside of the Matter SDK tree, follow the design pattern of scripts/py_matter_idl/examples/matter_idl_plugin:

1. Create a directory for your python generator module, for example “matter_idl_plugin”.
2. Add an __init__.py under “matter_idl_plugin” implementing a subclass of CodeGenerator named CustomGenerator.
3. Have CustomGenerator load jinja templates, also under the “matter_idl_plugin” subdirectory.
4. Execute the codegen.py script passing the path to the parent directory of “matter_idl_plugin” via --generator custom:<plugin_path>:<plugin_module_name> argument and package name like --option package:com.example.matter.proto

# From top-of-tree in this example
./scripts/codegen.py \
  --generator custom:./scripts/py_matter_idl/examples:matter_idl_plugin \
  --option package:com.example.matter.proto \
  ./src/controller/data_model/controller-clusters.matter