feat: Add Configuration and Implementation for Kafka Notifications

[myronjhicks]

This enhancement will enable the ACH Gateway to send a structured event over Kafka (in addition to email, slack, and pager duty) for consumption when such events occur.

The kafka is not currently included in the multi sender functionality of multi.go

This feature will enhance the observability and real-time monitoring capabilities of the ACH Gateway by leveraging Kafka's distributed messaging system.

Consumers of these Kafka events can themselves process, store, or add additional alerting based on the data in the struct.

[myronjhicks]

Promising but closed PR: #146

[myronjhicks]

Consideration: Following the FileUploaded events, could we also emit a MergedFileUploaded that is the struct from marshalKafkaMessage

[adamdecaf]

I don't remember why this wasn't added into multi.go, but I'm fine adding it. I remember that we didn't settle on the fields to return as part of the event, but what's there is probably fine.

I don't understand what MergedFileUploaded is. We'd publish FileUploaded, right?