[Bug] Do not support latest FOSSBILLING Version

[Tdnshah]

Describe the bug
This server manager needs to be updated to support latest fossbilling server manager api, currently it give internal server 500 error upon visiting Add server page in fossbilling backend.

To Reproduce
Steps to reproduce the behavior:

1. Add/install this virtualmin server as mentioned in the readme.
2. Open Fossbilling admin backend and try to visit {domain}/admin/servicehosting by clicking system in the main menu and Hosting and Plans in the drop down.
3. Upon visiting step 3 you will get an error Internal Server 500

Expected behavior
Should allow us to add plans and virtualmin server on which accounts needs to be created.

[jsonkenyon]

This version is actually currently unmaintained. Though I have forked it and got it working in https://github.com/NerdbyteIO/Virtualmin

I'm currently looking for testers to use it and report back on that repo, and if all is good I'll put in a PR to get this one updated and also maintain it.

[Tdnshah]

Ahh i was also working on fixing the issue an making it compatible with the latest code, awesome that you have already done it, i can help you testing you version will add my test results on your fork hope that works? Once again thank you for making this work :)

[jsonkenyon]

Indeed, thanks 🙏