Add invite route.

[Menrath]

Add /_matrix/client/r0/rooms/{roomId}/invite route.

See https://spec.matrix.org/legacy/r0.0.0/client_server.html#post-matrix-client-r0-rooms-roomid-invite.

Related to: https://tracker.moodle.org/browse/MDL-84293

[andrewnicols]

Technically the API user needs to be a member of the room to do the invite, but I don't think that we currently have them in the virtual room.

This is something that we may need to add in future.

This change is mostly good otherwise aside from some coding style issues. The main thing that is missing is that it doesn't actually do what it needs to do - that is it does not invite the user into the room!

[andrewnicols]

Also can you please squash the commits. We don't need to break things apart - it serves no purpose or benefit, and can be confusing when tracking bugs.

[Menrath]

@andrewnicols Thanks for reviewing this so quickly. I was not expecting this as there are very few guidelines for contributors. I also did not know what coding style to use, I could not find it explicitly stated in the repository. Adding that would help, and maybe I would have started contributing earlier! :)

I agree with your changes and will try to merge them in a minute. And of course I can squash them right away, unless you prefer to do a squash on the merge.