* Mark used and unused APIs by versions.
* remove the conditional invocations.
* isValid() and test updates.
* isValid() and tests.
* Remove warning logs for invalid user requests. Also, downgrade visibility.
* Update resp message, etc.
* tests and some cleanup.
* Docs draft
* Clarify docs
* Update server/src/main/java/org/apache/druid/server/http/DataSourcesResource.java
Co-authored-by: Kashif Faraz <kashif.faraz@gmail.com>
* Review comments
* Remove default interface methods only used in tests and update docs.
* Clarify javadocs and @Nullable.
* Add more tests.
* Parameterized versions.
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Co-authored-by: Kashif Faraz <kashif.faraz@gmail.com>