Add Identity environment variables for multi-tenancy and clients

[conceptualshark]

Description

Resolves https://github.com/camunda/camunda-docs/issues/3446

Adds environment variables around configuring multi-tenancy options to the Identity configuration. Will backport to 8.6 when the content is technically accurate.

This is a draft, as I am unsure if this list is complete or if these descriptions are accurate. Looking for feedback on that!

When should this change go live?

• [ ] This is a bug fix, security concern, or something that needs urgent release support. (add bug or support label)
• [x] This is already available but undocumented and should be released within a week. (add available & undocumented label)
• [ ] This is on a specific schedule and the assignee will coordinate a release with the DevEx team. (create draft PR and/or add hold label)
• [x] This is part of a scheduled alpha or minor. (add alpha or minor label)
• [ ] There is no urgency with this change (add low prio label)

PR Checklist

• [ ] My changes are for an upcoming minor release and:
  • [ ] are in the /docs directory (version 8.8).
  • [x] are in the /versioned_docs/version-8.7/ directory (version 8.7).
• [x] My changes are for an already released minor and are in a /versioned_docs directory.

• [ ] I added a DRI, team, or delegate as a reviewer for technical accuracy and grammar/style:
  • [ ] Engineering team review
  • [ ] Technical writer review via @camunda/tech-writers unless working with an embedded writer.

[github-actions[bot]]

:wave: :robot: :thinking: Hello, @christinaausley! Did you make your changes in all the right places?

These files were changed only in docs/. You might want to duplicate these changes in versioned_docs/version-8.7/.

• docs/apis-tools/testing/utilities.md

These files were changed only in versioned_docs/version-8.7/. You might want to duplicate these changes in docs/.

• versioned_docs/version-8.7/self-managed/identity/miscellaneous/configuration-variables.md
• versioned_docs/version-8.7/self-managed/operational-guides/configure-multi-tenancy.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]

@jwulf with your experience here, would you be able to help @conceptualshark confirm this info is correct?

[akeller]

I have not had time to revisit this and respond to the feedback. @camunda/tech-writers if you can pick this up and make progress on it while I'm out, please do.

[christinaausley]

@romansmirnov I think a few of these comments just require one final review from you, and then I can tidy this PR and get final approval from tech writers to merge 👍

[CLAassistant]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you all sign our Contributor License Agreement before we can accept your contribution.
1 out of 2 committers have signed the CLA.

:white_check_mark: christinaausley
:x: Cole Garbo

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[christinaausley]

I will open a new PR with these changes 👍

[christinaausley]

Closing in favor of https://github.com/camunda/camunda-docs/pull/5898.

[github-actions[bot]]

:broom: Preview environment for this PR has been torn down.