A partial log_config (no "version" key) is deep-merged over uvicorn's
default config before our patching, so users pass only their
customizations, e.g. log_config={"loggers": {"myapp": {"level":
"DEBUG"}}}. Previously such dicts crashed at startup: dictConfig
requires a version, and our root entry referenced a "default" handler
that might not exist; that reference is now only added when the handler
exists. The stock default formatter is replaced only when untouched,
so an overlaid fmt survives. Dicts with version and non-dict configs
behave as before. Documented in the README logging section, with tests
under fastapi-vue/tests (each patched config validated through
dictConfig).
LeoVasanko