How to retrieve LTI message claims and handle multiple LTI providers?

[dmilne-uts]

Hi there,

This is not so much an issue as a plea for help. I hope this is an appropriate place for that, but if not please let me know where else I should go.

I've successfully got the demo project up and running and talking to canvas, but I don't know how to proceed from there. Do you have any advice/pointers for how to:

1. retrieve details of the canvas course or user roles in a controller? The demo shows how to get the user name and sub, and it was pretty easy to extract the rest of the standard user identity claims, but it's not clear how to retrieve any of the other message claims mentioned in the LTI standard.
2. extend the demo so that it can register with multiple providers at the same time, as a live process? The demo requires the details of a specific provider in config/application.properties so it seems to be built with an assumption that there will only be one provider and it will be known at build time.

Thanks!
Dave