[DOCS][ESQL][8.14] Add API key based security model info for ESQL CCS

[leemthompo]

Note

This PR targets 8.14 changes first, updates for 8.15+ will come in follow-up PR.

Part 1 of tackling #108735.

URL preview

Drive-by edits 🚗

• Replace querying cluster and fulfilling cluster with local and remote for consistency
• Fix heading levels

[github-actions]

Documentation preview:

• ✨ Changed pages

[elasticsearchmachine]

Pinging @elastic/es-docs (Team:Docs)

[jakelandis]

looking good ... a couple of comments.

[leemthompo]

Thanks @jakelandis, I've updated per review

[edit] I also tried to add a little practical color for choosing between security models in 9e61001

c429b95 adds cluster privilege that is required in 99% of cases as we discussed

[jakelandis]

updates look good. a couple more suggestions.

[jakelandis]

Suggested change

	TLS certificate authentication makes sense in single administrator scenarios where you have full control over both clusters.
	TLS certificate authentication secures remote clusters with mutual TLS and is available under the basic license. This may be the preferred model where a single administrator has full control over both clusters.

[leemthompo]

Do we talk about licenses explicitly in docs given variance between self-managed and cloud?

[jakelandis]

I don't know our general stance, but it seems like an important detail since ES|QL is not gated by an enterprise license. IIUC in cloud user have access to all features, but are billed based on usage.

[leemthompo]

We use generic messaging about licensing as a rule, and the main pages for these security models have prerequisites sections that say stuff like "The local and remote clusters must have an appropriate license. For more information, refer to https://www.elastic.co/subscriptions". So I will refrain from mentioning licensing in this doc.

[leemthompo]

thanks @jakelandis! updated again, and tried to make some things more explicit about this doc, i.e. here we detail esql specifics but need to follow the full flow on the main API key authentication page

You can use the URL preview to check how the page looks and zoom out from the commit diffs

[jakelandis]

LGTM - a couple minor clarifications.

Thanks for working on this !

[elasticsearchmachine]

💚 Backport successful

Status	Branch	Result
✅	8.14