Feature: add sasl_oauthbearer support

[filip-danieluk]

Hi!

Faststream doesn't allow to authenticate with Oauth. According to librdkafka/CONFIGURATION.md sasl.mechanism must be set to OAUTHBEARER. However this value will get overwritten when specifying it in config and providing it during broker creation. To be precise it will get overwritten by one of _parse_* functions in faststream\confluent\security.py depending on which security class from faststream\security.py will be chosen. Changes should allow broker configuration with oauth:

broker = KafkaBroker(
    "host:port",
    config=config,
    security=SASLOAuthBearer(use_ssl=True),
)

To achieve this we need to implement a new security class and new parser. I have already created fork with these changes and successfully deployed it.

[filip-danieluk]

PR resolving the issue #1632