…_fields (#45)

Python logging config supports access to
[external](https://docs.python.org/3/library/logging.config.html#access-to-external-objects)
and
[internal](https://docs.python.org/3/library/logging.config.html#access-to-internal-objects)
objects via
[DictConfiguator](https://docs.python.org/3/library/logging.config.html#configuration-functions)
prefixes.

This works internally by warpping the dict with a
[ConvertingDict](https://github.com/python/cpython/blob/main/Lib/logging/config.py#L337)
that requires an explicit call to it's
[\_\_getitem\_\_](https://github.com/python/cpython/blob/main/Lib/logging/config.py#L340)
dunder method for the
[conversion](https://github.com/python/cpython/blob/main/Lib/logging/config.py#L307)
to take place (using the specific converter for the specified prefix).

This allows, for example, having a *log_config.yaml* file like:

```yaml
version: 1
disable_existing_loggers: False
formatters:
  default:
    "()": pythonjsonlogger.json.JsonFormatter
    format: "%(asctime)s %(levelname)s %(name)s %(module)s %(funcName)s %(lineno)s %(message)s"
    rename_fields:
      "asctime": "timestamp"
      "levelname": "status"
    static_fields:
      "service": ext://logging_config.PROJECT_NAME
      "env": ext://logging_config.ENVIRONMENT
      "version": ext://logging_config.PROJECT_VERSION
      "app_log": "true"
handlers:
  default:
    formatter: default
    class: logging.StreamHandler
    stream: ext://sys.stderr
  access:
    formatter: default
    class: logging.StreamHandler
    stream: ext://sys.stdout
loggers:
  uvicorn.error:
    level: INFO
    handlers:
      - default
    propagate: no
  uvicorn.access:
    level: INFO
    handlers:
      - access
    propagate: no
```

where *service*, *env* and *version* values are taken from the external
resource *logging_config.py*.

The content for *logging_config.py* could be something like (for getting
some values from project metadata or environment variables):

```python
import importlib.metadata
import os


def get_version_metadata():
    # https://stackoverflow.com/a/78082532
    version = importlib.metadata.version(PROJECT_NAME)
    return version


PROJECT_NAME = 'test-api'
PROJECT_VERSION = get_version_metadata()
ENVIRONMENT = os.environ.get('ENVIRONMENT', 'dev')
```

---------

Co-authored-by: Nicholas Hairs <info@nicholashairs.com>

Per title

Various minor fixes as suggested by jules.google

---------

Co-authored-by: google-labs-jules[bot] <161369871+google-labs-jules[bot]@users.noreply.github.com>

Per title

---------

Co-authored-by: google-labs-jules[bot] <161369871+google-labs-jules[bot]@users.noreply.github.com>

#60)