* and stop setting default values in python operator code, so defaults can be set at the server side.

This issue is just for the PR and questions from maintainers. 
setup.py
"""The setuptools.Distribution subclass with Airflow specific behaviour"""
    def parse_config_files(self, *args, **kwargs) -> None:
        """
        Ensure that when we have been asked to install providers from sources
        that we don't *also* try to install those providers from PyPI.
        Also we should make sure that in this case we copy provider.yaml files so that
        Providers manager can find package information.
        """
        super().parse_config_files(*args, **kwargs)
        if os.getenv(INSTALL_PROVIDERS_FROM_SOURCES) == 'true':
            self.install_requires = [
                req for req in self.install_requires if not req.startswith('apache-airflow-providers-')
            ]
            provider_yaml_files = glob.glob("airflow/providers/**/provider.yaml", recursive=True)
            for provider_yaml_file in provider_yaml_files:
                provider_relative_path = relpath(provider_yaml_file, os.path.join(my_dir, "airflow"))
                self.package_data['airflow'].append(provider_relative_path)
        else:
            self.install_requires.extend(
                [get_provider_package_from_package_id(package_id) for package_id in PREINSTALLED_PROVIDERS]
            )
def replace_extra_requirement_with_provider_packages(extra: str, providers: List[str]) -> None: