add reproduction test case for dynamic template bug

[rursprung]

this adds a test case to reproduce #1513
essentially this is a port of opensearch-project/spring-data-opensearch#443 which purely uses the opensearch-java APIs rather than going through the Spring APIs.

this does not attempt to fix the bug, it just adds an ignored test case which will make it easier to reproduce & fix the bug.

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CC @reta: i ported your PR

[rursprung]

the changelog is intentionally not updated as this doesn't change anything in the client itself, please add the skip changelog label

[reta]

the changelog is intentionally not updated as this doesn't change anything in the client itself, please add the skip changelog label

Thanks @rursprung , I will remove @Ignore from the test case so we could possibly come up with the fix

[rursprung]

Thanks @rursprung , I will remove @Ignore from the test case so we could possibly come up with the fix

but then we can't merge the PR because the tests fail, right? my hope was that the PR can be merged so that the test is there and shows that something is amiss. otherwise it'll suffer the same fate as your PR original: it'll just hang around as a stale PR and eventually run into merge conflicts.

[reta]

but then we can't merge the PR because the tests fail, right? my hope was that the PR can be merged so that the test is there and shows that something is amiss. otherwise it'll suffer the same fate as your PR original: it'll just hang around as a stale PR and eventually run into merge conflicts.

Thanks @rursprung , I believe we need to fix the issue, the test will be "dead body", plus those are new files - there is no risk of any merge conflicts