[Go SDK]: Implement natsio.Read transform for reading from NATS

[johannaojeling]

Implements a natsio.Read transform for reading from NATS JetStream. Fixes #29000.

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[johannaojeling]

R: @lostluck

I have taken inspiration from unbounded sources/SDFs in the Java SDK (KafkaIO, PulsarIO, etc.) and have tried to keep it simple in this first iteration. It is the first streaming connector I write so let me know if there are any best practices I'm missing out on.

[github-actions]

Stopping reviewer notifications for this pull request: review requested by someone other than the bot, ceding control

[codecov]

Codecov Report

Attention: 80 lines in your changes are missing coverage. Please review.

Comparison is base (d24c40a) 37.99% compared to head (8af3489) 37.95%.
Report is 1 commits behind head on master.

❗ Current head 8af3489 differs from pull request most recent head b49d27f. Consider uploading reports for the commit b49d27f to get more accurate results

Files	Patch %	Lines
sdks/go/pkg/beam/io/natsio/read.go	69.86%	33 Missing and 11 partials ⚠️
sdks/go/pkg/beam/io/natsio/read_option.go	33.33%	21 Missing and 3 partials ⚠️
sdks/go/pkg/beam/io/natsio/end_estimator.go	78.12%	5 Missing and 2 partials ⚠️
sdks/go/pkg/beam/io/natsio/common.go	0.00%	2 Missing and 1 partial ⚠️
sdks/go/pkg/beam/io/natsio/time_policy.go	83.33%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master   #29410      +/-   ##
==========================================
- Coverage   37.99%   37.95%   -0.05%     
==========================================
  Files         691      695       +4     
  Lines      101309   101499     +190     
==========================================
+ Hits        38497    38520      +23     
- Misses      61213    61366     +153     
- Partials     1599     1613      +14     

Flag	Coverage Δ
go	53.47% <66.10%> (-0.09%)	⬇️

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[lostluck]

Thank you for your patience for the delay in reviewing. I've been distracted with chasing flakes with Prism, and have also fallen sick. It's going to take a little longer.

[johannaojeling]

Thank you for your patience for the delay in reviewing. I've been distracted with chasing flakes with Prism, and have also fallen sick. It's going to take a little longer.

No worries, hope you feel better soon!

[lostluck]

Thanks for your patience!

As always, your code remains a delight to read. I don't have much to add, as AFAICT you're using all the parts correctly. The trick is whether different runners split in a reasonable fashion (specifically Prism, which will probably be very aggressive).

[lostluck]

OK, so this means no initial splits, so a single stream to start, and only dynamic splits will occur. I think this is correct WRT the rest of the code.

[johannaojeling]

Thanks for your patience!

As always, your code remains a delight to read. I don't have much to add, as AFAICT you're using all the parts correctly. The trick is whether different runners split in a reasonable fashion (specifically Prism, which will probably be very aggressive).

Thank you for reviewing! I resolved the conflict in CHANGES.md, so if you are happy it should be good to merge. It was fun to learn more about unbounded sources 😊

[damccorm]

Looks like there's another conflict in CHANGES.md unfortunately, @johannaojeling would you mind resolving again? @lostluck is this good to merge otherwise?

[lostluck]

Thank you for your patience WRT merging it in. Thanks Danny for the reminder!