Add identity request management in gateway

[koevskinikola]

Description

Document the Identity request management feature in the Zeebe Gateway. Since the configuration properties for this feature are experimental, we are not documenting them directly, but onlt linking to the YAML configuration templates in the camunda/camunda repository. This follows the same documentation pattern as the Broker's experimental configuration properties.

ℹ️ This PR documents the code added through the following PRs:

• Fix identity-sdk concurrency issue camunda#24196
• [Backport stable/8.5] Fix identity-sdk concurrency issue camunda#24270
• [Backport stable/8.4] Fix identity-sdk concurrency issue camunda#24269

The fix must be released with the upcoming 8.6.x, 8.5.y, and 8.4.4 patch releases. Due to Identity's re-architecture, the bug won't be present in 8.7 so no need to document it there.

closes #4546

When should this change go live?

• This is a bug fix, security concern, or something that needs urgent release support.
• This is already available but undocumented and should be released within a week.
• This on a specific schedule and the assignee will coordinate a release with the DevEx team. (apply hold label or convert to draft PR)
• This is part of a scheduled alpha or minor. (apply alpha or minor label)
• There is no urgency with this change and can be released at any time.

PR Checklist

• My changes are for an already released minor and are in /versioned_docs directory.
• My changes are for the next minor and are in /docs directory (aka /next/).

• My changes require an Engineering review, and I've assigned the Engineering DRI or delegate.
• My changes require a technical writer review, and I've assigned @camunda/tech-writers as a reviewer.

[github-actions]

👋 🤖 🤔 Hello! Did you make your changes in all the right places?

These files were changed only in versioned_docs/version-8.6/. You might want to duplicate these changes in docs/.

• versioned_docs/version-8.6/self-managed/zeebe-deployment/configuration/gateway.md
• versioned_docs/version-8.6/self-managed/zeebe-deployment/operations/backpressure.md

You may have done this intentionally, but we wanted to point it out in case you didn't. You can read more about the versioning within our docs in our documentation guidelines.

[akeller]

The fix must be released with the upcoming 8.6.x, 8.5.y, and 8.4.4 patch releases. Due to Identity's re-architecture, the bug won't be present in 8.7 so no need to document it there.

Thank you for this!

[conceptualshark]

I moved the backpressure note to the end of the introduction if that's alright, but this is otherwise good to go on my end. 👍

I'll keep an eye on this for when it receives engineering approval, and can cut a release to the docs site then.

[remcowesterhoud]

No comments from my side 👍

[conceptualshark]

Thanks for the version fix - let me know if you'd like this released once it's merged.

[koevskinikola]

Hey @conceptualshark, yes, releasing this as soon as it is merged would be great, thanks!