Replace RxJava 2 with RxJava 3.

[wilx]

Description

I have started to use the client and it works well for me. But one thing of concern for me is that it uses unmaintained RxJava2. I was wondering if it can be easily replaced. It looks like it mostly is easily replaced.

I did not do any heavy testing though. And one IT test fails locally for me due to some Docker pull error.

I was wondering if you had any plans for moving forward with such RxJava upgrade?

Related Issue

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)
• [x] 💥 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.

[cla-bot[bot]]

Thank you for your pull request and welcome to our community. We require contributors to sign our Contributor License Agreement, and we don't seem to have the users @wilx on file. In order for us to review and merge your code, please sign our Contributor License Agreement to get yourself added. You'll find the CLA and more information here: https://github.com/hivemq/hivemq-community/blob/master/CONTRIBUTING.adoc#contributor-license-agreement

[cla-bot[bot]]

Thank you for your pull request and welcome to our community. We require contributors to sign our Contributor License Agreement, and we don't seem to have the users @wilx on file. In order for us to review and merge your code, please sign our Contributor License Agreement to get yourself added. You'll find the CLA and more information here: https://github.com/hivemq/hivemq-community/blob/master/CONTRIBUTING.adoc#contributor-license-agreement