#19191 made me realise the DefaultReplicationWorker's metric tracking today has a bug where we aren't accounting for namespace when tracking metrics today. i.e. Streams with the same name and duplicate namespace will merge metrics.
While reading the code to figure out a fix, I realised we don't have a good conceptual representation of stream namespace <> name pairs within the platform today. We use a concatenated string. Though this works, it will become harder and harder to read/track as we do more operations that involve namespace i.e. progress bars and column selection.
This PR introduces the AirbyteStreamNameNamespacePair object into the platform code to make it more convenient to work with Streams in the future. (Especially if we proceed with the project to make streams a first-class citizen!)
The AirbyteStreamNameNamespacePair object was written to deal with the same issue of namespace <> name pair manipulation within the Java destination code. It implements the Comparable interface, which makes it convenient to use for Collections operations.
For an example of how this is consumed, see #19361.
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