Deprecate namespaces no longer in API spec

[kimpepper]

Description

Deprecates namespaces no longer in the API spec.

Unfortunately there is no way to deprecate the corresponding methods in the Client as the template doesn't support this.

Issues Resolved

#262

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[kimpepper]

The 'Unreleased Opensearch' build fail looks unrelated:

Could not compile settings file '/home/runner/work/opensearch-php/opensearch-php/opensearch/settings.gradle'.
> startup failed:
  General error during semantic analysis: Unsupported class file major version 65

[dblock]

The 'Unreleased Opensearch' build fail looks unrelated:

Could not compile settings file '/home/runner/work/opensearch-php/opensearch-php/opensearch/settings.gradle'.
> startup failed:
  General error during semantic analysis: Unsupported class file major version 65

There was a JDK update in opensearch-project/OpenSearch#17144 which was a patch release and shouldn't have caused this. @reta any ideas?

[reta]

There was a JDK update in opensearch-project/OpenSearch#17144 which was a patch release and shouldn't have caused this. @reta any ideas?

This is surprising (Gradle for PHP projects) but yeah @dblock , we need to bump the source / target level to JDK-21, I will try to help out shortly Figured out this is a GA workflow, fixing it