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
with unittest.mock.patch.dict('os.environ'):
            if 'AIRFLOW_CONFIG' in os.environ:
                del os.environ['AIRFLOW_CONFIG']
            assert get_airflow_config('/home/airflow') == expand_env_var('/home/airflow/airflow.cfg')
    def test_airflow_config_override(self):
        with unittest.mock.patch.dict('os.environ', AIRFLOW_CONFIG='/path/to/airflow/airflow.cfg'):
            assert get_airflow_config('/home//airflow') == '/path/to/airflow/airflow.cfg'
    @conf_vars({("core", "percent"): "with%%inside"})
    def test_case_sensitivity(self):
        
        
        assert conf.get("core", "percent") == "with%inside"
        assert conf.get("core", "PERCENT") == "with%inside"
        assert conf.get("CORE", "PERCENT") == "with%inside"
    def test_env_var_config(self):
        opt = conf.get('testsection', 'testkey')
        assert opt == 'testvalue'
        opt = conf.get('testsection', 'testpercent')
        assert opt == 'with%percent'
        assert conf.has_option('testsection', 'testkey')
        with unittest.mock.patch.dict(
            'os.environ', AIRFLOW__KUBERNETES_ENVIRONMENT_VARIABLES__AIRFLOW__TESTSECTION__TESTKEY='nested'
        ):
            opt = conf.get('kubernetes_environment_variables', 'AIRFLOW__TESTSECTION__TESTKEY')
            assert opt == 'nested'
    @mock.patch.dict(
        'os.environ', AIRFLOW__KUBERNETES_ENVIRONMENT_VARIABLES__AIRFLOW__TESTSECTION__TESTKEY='nested'
    )
    @conf_vars({("core", "percent"): "with%%inside"})
    def test_conf_as_dict(self):