[FLINK-29042][Connectors/ElasticSearch] Support lookup join for es connector

[liyubin117]

Now es connector could only be used as a sink, but in many business scenarios, we treat es as a index database, thus we should support to make it lookupable in flink.

[boring-cyborg]

Thanks for opening this pull request! Please check out our contributing guidelines. (https://flink.apache.org/contributing/how-to-contribute.html)

[liyubin117]

@MartijnVisser Hi. Could you please give a review? Thanks!

[MartijnVisser]

@vahmed-hamdy Since you offered to volunteer to review an Elasticsearch PR, perhaps you could also have a look at this open PR?

[liyubin117]

@MartijnVisser @vahmed-hamdy Hi, The feature has taken effect in our production environment for one more years, now we want to updrade our es connector, if the feature would be merged, it would be very nice to upgrade directly!

[MartijnVisser]

@reta Do you have any considerations before merging this?

[reta]

@reta Do you have any considerations before merging this?

@MartijnVisser LGTM, we would probably could bring that to OpenSearch connector as well, thank you!

[snuyanzin]

Suggested change

	return "Elasticsearch-6";
	return "Elasticsearch6";

There is DynamicSink with Elasticsearch6, shouldn't we follow same naming conventions?

flink-connector-elasticsearch/flink-connector-elasticsearch6/src/main/java/org/apache/flink/streaming/connectors/elasticsearch/table/Elasticsearch6DynamicSink.java

Lines 197 to 199 in ce44a13

	public String asSummaryString() {
	return "Elasticsearch6";
	}

[liyubin117]

wise consideration 👍

[snuyanzin]

thanks for the contribution
also looks good from my side
i left some minor comments

+1 for having similar things for OpenSearch

[MartijnVisser]

@snuyanzin Will you take care of the rest of the review and merge it when you think it's OK?

[snuyanzin]

yes, sure, will try to do it later today/tomorrow

[liyubin117]

CI failed caused by outdated dev branch, I have rebased on the latest main branch and CI succeed.
@snuyanzin PTAL, Thanks very much!

[snuyanzin]

Thanks for addressing comments

[boring-cyborg]

Awesome work, congrats on your first merged pull request!

[liyubin117]

@snuyanzin @MartijnVisser @reta Thanks a lot for your patient work.