Configuration: schema and migration system

[tony]

config - system for deprecating old configs

config.schema - schema

• dataclasses
• typed dicts
• shapes
• whatever it takes to take a dict-like structure

config.v - old versions config/v/ - an old version is tagged whenever new one is config/v/tests/test_config.py tests / assertions for schema to migrate to new one, load old ones with deprecation warning