BATCH message type preview feedback

[aaronsteers]

As of v0.11.0, SDK now supports BATCH messages in preview status.

Resources:

• Launch PR: feat: Add support for new BATCH message type in taps and targets #904
• SDK Docs link: https://meltano-sdk--904.org.readthedocs.build/en/904/batch.html

Please use this discussion to log your feedback and other observations in regards to this new spec extension.

You can also join us in Slack (https://meltano.com/slack) in the channels #singer-tap-development and #singer-target-development.

[aaronsteers]

Wanted to call out for discussion: we currently have an overloaded meaning of 'batch' which we may want to resolve and/or clarify in future. BatchSink is a subclass of Sink that wants to load its items in bulk. "Batch messages" are a means of taps and targets communicating via sending of files.

It's possible we could refactor the BATCH message handler to use a common codebase with BatchSink but either way, and just in general, we should probably think on how to make sure these concepts are not conflated. Also, if the two are not already leveraging a shared codepath for things like batch flush logic, it might be worth considering. (I don't have strong feelings about this, to be clear. Just wanted to raise for discussion.)

cc @edgarrmondragon