Make management-port required

[akshan-main]

Before this PR

management-port was optional. If left out, status endpoints got served on the main port. That fallback existed for the migration to a dedicated management port, which is done. See #281.

After this PR

==COMMIT_MSG==
management-port is required in install config.
==COMMIT_MSG==

Possible downsides?

Breaking config change. Any service still omitting management-port will fail to start until it's added. Also updated the example in the crate docs so it doesn't show a stale config without the field.

[changelog-app]

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Type (Select exactly one)

• Feature (Adding new functionality)
• Improvement (Improving existing functionality)
• Fix (Fixing an issue with existing functionality)
• Break (Creating a new major version by breaking public APIs)
• Deprecation (Removing functionality in a non-breaking way)
• Migration (Automatically moving data/functionality to a new system)

Description

management-port is now required in install configuration.

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[akshan-main]

@sfackler saw your issue #281 and thought I could contribute

[sfackler]

Thanks for the PR! I do want to land this, but since it's a breaking change I'd like to hold off to bundle it with other breaks.

[akshan-main]

@sfackler Sounds good, thanks! I’ll leave this open and can rework it whenever it makes sense to bundle the breaking changes.

Also, I’m trying to get more involved in OSS and would be glad to take on more substantive work if there are issues where an outside contributor could be useful. I’m especially interested in Rust server internals, async/concurrency, config/runtime behavior. Feel free to tag me, and I can help by contributing.