added graalvm native image reflect config for a seamless experience

[cmdjulian]

Description

This changes adds the required graalvm reflection config for the two missing fields. This config is picked up by graalvm during native compilation and registers the two fields for reflective access on the compiled native image java app.
See here for more details.

Related Issue

#448

Type of Change

• 📚 Examples / docs / tutorials / dependencies update
• 🔧 Bug fix (non-breaking change which fixes an issue)
• 🥂 Improvement (non-breaking change which improves an existing feature)
• 🚀 New feature (non-breaking change which adds functionality)
• 💥 Breaking change (fix or feature that would cause existing functionality to change)
• 🔐 Security fix

Checklist

• I've written tests (if applicable) for all new methods and classes that I created.
• I've added documentation as necessary so users can easily use and understand this feature/fix.

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[cmdjulian]

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[SgtSilvio]

Thank you for your contribution @cmdjulian!
In general, it would be best if JCTools would ship with the right native image configuration. As JCTools is only a dependency, the user of the hivemq-mqtt-client can update the JCTools version transitively which might need a change in the native image configuration as well.
But I agree that we can at least make the user experience better.
I am unsure if reflective access is the right thing here. We have the hivemq-mqtt-client running in a native image as part of the mqtt-cli, where we --initialize-at-build-time the JCTools classes, see https://github.com/hivemq/mqtt-cli/blob/master/build.gradle.kts#L416.
Maybe we can just include these settings instead of the reflection config?

[cmdjulian]

Yeah you right. Thanks for pointing this out.
I had a look at JCTools, and is seems like they use a lot of reflection and Unsafe. I was thinking about contributing a PR over there as well, maybe I find some time in the future to do so.