Directly adding fields to json log when log has parameterized string

is something like this possible
example:
```
addItem='abcd'
logger.info(f"added todo item {addItem} to the todo list")
```
*note: or any way of adding parametrized string
log:
`{'name': 'app.routes.controller', 'msg': 'added todo item abcd to the todo list', 'args': (), 'levelname': 'INFO', 'levelno': 20, 'fields': {'addItem': 'abcd'}}`

No file, test, or entry point is identified in the issue. Start by locating the logger API and its handling of parameterized messages and structured fields; done means the requested fields can be emitted alongside the formatted message, with tests covering the example behavior.

Written by the indexing model from the issue text.