[FLINK-22791][docs] Documentation for HybridSource

[tweise]

Initial documentation for HybridSource (introduced in #15924).

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[SteNicholas]

Is it better to explain that this Source is a better point based on FLIP-27?

[AHeise]

I'd not explicitly mention FLIP-27. Eventually source=FLIP-27, if we do a good enough job. But maybe we could link to https://ci.apache.org/projects/flink/flink-docs-release-1.13/docs/dev/datastream/sources/?

[tweise]

+1, added the link

[AHeise]

Added some smaller suggestions.

[AHeise]

I'd not explicitly mention FLIP-27. Eventually source=FLIP-27, if we do a good enough job. But maybe we could link to https://ci.apache.org/projects/flink/flink-docs-release-1.13/docs/dev/datastream/sources/?

[tweise]

Thanks for the review and suggestions!

@AHeise PTAL

[AHeise]

LGTM. Thank you very much.

I'm wondering if we should also tease the HybridSource in the overview page. https://ci.apache.org/projects/flink/flink-docs-release-1.13/docs/connectors/datastream/overview/
It's very special since it's our first secondary source and folks may not know that they need it.

[tweise]

I'm wondering if we should also tease the HybridSource in the overview page. https://ci.apache.org/projects/flink/flink-docs-release-1.13/docs/connectors/datastream/overview/
It's very special since it's our first secondary source and folks may not know that they need it.

Good idea, I will take a look.