Feature: GSSAPI (Kerberos) support

[roma-frolov]

Hi there!

Kafka supports the Kerberos authentication protocol. Currently, Faststream does not explicitly specify a security mechanism for GSSAPI.

Now, in order for the broker to work with Kafka servers with Kerberos authentication, you have to do this:

broker._connection_kwargs.update(
    {
        "security_protocol": "SASL_SSL",
        "sasl_mechanism": "GSSAPI",
        "ssl_context": create_ssl_context(),
    },
)

I suggest creating a SASLGSSAPI class in faststream/security.py:

class SASLGSSAPI(BaseSecurity):
    """Security configuration for SASL/GSSAPI authentication.

    This class defines security configuration for SASL/GSSAPI authentication.
    """

    def __init__(
        self,
        ssl_context: Optional["SSLContext"] = None,
        use_ssl: Optional[bool] = None,
    ) -> None:
        super().__init__(
            ssl_context=ssl_context,
            use_ssl=use_ssl,
        )

    def get_requirement(self) -> List["AnyDict"]:
        """Get the security requirements for SASL/GSSAPI authentication."""
        return [{"gssapi": []}]

    def get_schema(self) -> Dict[str, Dict[str, str]]:
        """Get the security schema for SASL/GSSAPI authentication."""
        return {"gssapi": {}}

and parsing in kafka/security.py (and the same parsing in confluent/security.py):

def _parse_sasl_gssapi(security: SASLGSSAPI) -> "AnyDict":
    return {
        "security_protocol": "SASL_SSL" if security.use_ssl else "SASL_PLAINTEXT",
        "ssl_context": security.ssl_context,
        "sasl_mechanism": "GSSAPI",
    }

This will allow you to specify the authentication method in this way without interfering with protected attributes:

broker = KafkaBroker(
    bootstrap_servers=[
        "example.ru:9092",
    ],
    sasl_kerberos_service_name="example_service_name",
    security=SASLGSSAPI(ssl_context=create_ssl_context(), use_ssl=True),
)

Well, I will also have to correct some shortcomings in specifying the sasl mechanism, for example these.
I'm ready to implement this feature.

[kumaranvpl]

@roma-frolov Yes, this security option is currently missing from FastStream.
If you think you can add it, please feel free to create a PR with your proposed changes.