Invitations system

[hponcet]

Hi guys, my name is Hugues and I'm happy to present you this pull request centered around plex invitations from the Petio interface.
I decided to make this feature because invitations on Plex are often complicated to explain and manage for an audience unfamiliar with the workings of these ecosystems.
I've tried to keep as much as possible to your habits and styles of code for the integration, but I expect a critical eye for any improvements or corrections. Especially with the XmlToJson library, which made me lose a few hairs.

Here's a photo presentation of the feature, and I'll let you see the urls to deduce the environment.

Thanks in advance for the review :)

[ADRFranklin]

Hello, sorry for the late reply, been quite busy with work and life.

This looks really good, definitely a worthy feature. I'm not quite sure yet if this is a feature that can currently work with the work going on with version 1, as I didn't have any plans to add more features to 0.5.x versions. The backend for version has been completely refactored and isn't remotely close to the current structure, so that is something that would need to be re-done to meet those requirements.

As for the frontend it looks good, but I'll let Ash comment on that one, and you can discuss any frontend changes with him. @AshDyson

I can't really give an ETA on the v1 release, but it is mostly all there, just finding more then a few hours to work on it, has been difficult lately, but hopefully I can find more time to work on it.

EDIT: Thinking more about it, I might be fine to merge this in for 0.5.7 and make a small release with some other fixes/patches while version 1 is still being worked on, I can always port the code over later myself, if needed. You'll still have to wait for Ash to give his feedback on the frontend, and the merge conflicts will need to be solved.

[hponcet]

Hi, no problemo, i wait for the instructions.