fix: kafka connection config in git integration v2

[mbani01]

This pull request refactors the Kafka producer configuration in the QueueService to make it more flexible and secure. The main improvement is that Kafka connection parameters (including SSL and SASL settings) are now dynamically loaded from the CROWD_KAFKA_EXTRA environment variable, allowing easier configuration changes without code updates.

Kafka configuration improvements:

• Refactored the initialization of the Kafka producer in QueueService to use a new _build_kafka_config method, which dynamically constructs the configuration based on the JSON in CROWD_KAFKA_EXTRA instead of hardcoding SASL/SSL parameters.
• Added support for SSL connections by conditionally setting security_protocol and ssl_context based on the configuration, increasing security and flexibility.
• Removed direct imports and usage of CROWD_KAFKA_USER and CROWD_KAFKA_PASSWORD in favor of extracting SASL credentials from the extra configuration, centralizing sensitive configuration management. [1] [2]

Checklist ✅

• Label appropriately with Feature, Improvement, or Bug.
• Add screenshots to the PR description for relevant FE changes
• New backend functionality has been unit-tested.
• API documentation has been updated (if necessary) (see docs on API documentation).
• Quality standards are met.

[epipav]

lgtm 👍