[FLINK-34441] Add guide to submit flink SQL scripts via the operator (using flink-sql-runner-example)

[prakash-42]

What is the purpose of the change

This pull request adds documentation about flink-sql-runner-example in the Kubernetes operator documentation page. Majority of the content is copied over from the flink-sql-runner-example's readme.

Brief change log

• Added guide to submit flink SQL scripts via the kubernetes operator (using flink-sql-runner-example)

Verifying this change

This change is a trivial rework / code cleanup without any test coverage.
I don't know if we have tests covering the docs project. I ran the project locally and made sure that my changes are being rendered properly.

Does this pull request potentially affect one of the following parts:

• Dependencies (does it add or upgrade a dependency): no
• The public API, i.e., is any changes to the CustomResourceDescriptors: no
• Core observer or reconciler logic that is regularly executed: no

Documentation

• Does this pull request introduce a new feature? no
• If yes, how is the feature documented? not applicable

[prakash-42]

@mxm Here is a PR for the discussion we were having at PR #596 . Please let me know if any updates/improvements are needed. Thank you!

[mxm]

Taking another look, this might not be the best place to add this information because it's an overview page and the steps are quite detailed. There is already a section mentioning the examples: https://nightlies.apache.org/flink/flink-kubernetes-operator-docs-main/docs/concepts/overview/#built-in-examples How about creating a dedicated Examples page?

[mxm]

I think we should avoid copying anything over from https://github.com/apache/flink-kubernetes-operator/tree/main/examples/. Instead, we can extract the above linked examples section to a dedicated page and add any extra information we find useful.

[prakash-42]

Thanks for the comments @mxm ! I agree that we should have a dedicated page for examples, instead of adding more in the overview page. However, I have a few follow-up concerns/questions:

1. If I don't copy over from the examples' readme, I'd still be needing to write content that's similar to whatever is present in the example's readme. I can try and make it short, while linking to the readme page for more details.

2. If I create a dedicated Examples page, then I think it shouldn't just have the Flink SQL example, but other examples as well. I will try and write a few more, but not sure if I have enough experience/knowledge to write about all the examples. Can we make this like a running doc where more examples will be added as the need arises?

3. One concern I have about linking to README pages is that I'm likely going to link to the examples in main branch, and that code may change with later releases in the operator. Would that possibly make the examples in the operator point to an incompatible readme? (I see that the existing links also point to the main branch, so maybe that's okay)