Feature Request: Support for Open Extensions

[Weishaupt]

Hey there, I'd love to see support for Open Type extensions. In my case I have a use case where I want to add custom data to calendar events.

Currently I use a mix of the python-o365 library and native python graph libraries from Microsoft to perform the required tasks.

This brings quite some overhead, and having native support for open type extensions within this library would make my life easier.

Thank you for your work.

[alejcas]

This can be added, but don't currently have the time to do it. PR are welcome.

Thanks