Hello,

In Airflow 2, we've moved some configuration options to the new section. We also changed the names of some of the configuration options. This is confusing for users who are familiar with the old option and section names.  It would be great if we could add information to the documentation that points to the new name of the options.

https://github.com/apache/airflow/blob/8f48f12128e0d985c6de2603902524859fecbca8/airflow/configuration.py#L139-L169

> 'The {old} option in [{section}] has been renamed to {new}
> 'The {old_key} option in [{old_section}] has been moved to the {new_key} option in '
> '[{new_section}]

Best regards,
Kamil Breguła

tests/core/test_configuration.py
assert conf.has_option("core", "FERNET_KEY")
        assert not conf.has_option("core", "FERNET_KEY_CMD")
        fernet_key = conf.get('core', 'FERNET_KEY')
        with conf_vars({('core', 'FERNET_KEY_CMD'): 'printf HELLO'}):
            fallback_fernet_key = conf.get("core", "FERNET_KEY")
        assert fernet_key == fallback_fernet_key
    def test_config_throw_error_when_original_and_fallback_is_absent(self):
        assert conf.has_option("core", "FERNET_KEY")
        assert not conf.has_option("core", "FERNET_KEY_CMD")
        with conf_vars({('core', 'fernet_key'): None}):
            with pytest.raises(AirflowConfigException) as ctx:
                conf.get("core", "FERNET_KEY")
        exception = str(ctx.value)
        message = "section/key [core/fernet_key] not found in config"
        assert message == exception
    def test_config_override_original_when_non_empty_envvar_is_provided(self):
        key = "AIRFLOW__CORE__FERNET_KEY"
        value = "some value"
        with mock.patch.dict('os.environ', {key: value}):
            fernet_key = conf.get('core', 'FERNET_KEY')
        assert value == fernet_key
    def test_config_override_original_when_empty_envvar_is_provided(self):
        key = "AIRFLOW__CORE__FERNET_KEY"
        value = "some value"
        with mock.patch.dict('os.environ', {key: value}):
            fernet_key = conf.get('core', 'FERNET_KEY')
        assert value == fernet_key
    @mock.patch.dict("os.environ", {"AIRFLOW__CORE__DAGS_FOLDER": "/tmp/test_folder"})
    def test_write_should_respect_env_variable(self):