docs: added x.509 docs for java clients

[igpetrov]

Description

Epic: https://github.com/camunda/product-hub/issues/2451

Added documentation to new security features for plain Java client and Spring SDK Java client.

When should this change go live?

Let's have it with 8.7.0-alpha3 under /next/ please.

• 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, @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-8.6/.

• docs/apis-tools/java-client/index.md
• docs/apis-tools/spring-zeebe-sdk/configuration.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.

[igpetrov]

👋 🤖 🤔 Hello, @igpetrov! 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-8.6/.

* docs/apis-tools/java-client/index.md

* docs/apis-tools/spring-zeebe-sdk/configuration.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.

Dear Bot, the changes are correct and expected to go the /next/. Thank you.

[christinaausley]

What is CA here, just to clarify?

[igpetrov]

Hi @christinaausley. Thank you for looking into it!
It's a Certificate Authority.

I didn't clarify it in the doc because I would expect that person who wants to configure X.509, should what CA is.