Instance config overrides are shallow: each provided top-level key replaces
the matching default config value. Nested objects are full replacements and
must contain the complete structure described by BaseConfig, except where
BaseConfig itself marks nested entries as partial.
Instance config overrides are shallow: each provided top-level key replaces the matching default config value. Nested objects are full replacements and must contain the complete structure described by BaseConfig, except where BaseConfig itself marks nested entries as partial.