Add Version to Template and Pipelines

[pickypg]

When writing code that needs to publish its own template(s) or pipeline(s), it can be a small burden to verify that the existing template version exists, especially if you ever make backward-compatible changes.

I propose that we add a completely optional version field to each template and pipeline that is 100% user-driven. If they don't supply it, then it doesn't exist. If they do supply it, then it exists as whatever value they set (regardless of what might have been there before!). The version will exist solely as a mechanism for client software to ensure that not only is their template or pipeline there, but it's the one that they submitted last time without having to go field-by-field.

This allows requests like this to be submitted:

GET /_template/.monitoring-es-2?filter_path=*.version

Then, the client can loop through the returned templates and only concern itself with the name and version. Pipelines would have an equivalent look:

GET /_ingest/pipelines/.monitoring*?filter_path=*.version

• Templates Add "version" field to Templates #20353
• Pipelines Add "version" field to Pipelines #20343

[martijnvg]

I removed the discuss label here. Since the proposed change here makes sense to me.

[pickypg]

merged in #20343 and #20353