Add Otel metrics to PAR implementation

[josephdecock]

No description provided.

[josephdecock]

@AndersAbel, after your work on OTEL metrics and my work on PAR both get merged, I think we want to add OTEL metrics to the PAR endpoint as well. Also, I didn't introduce new events for PAR, or emit any existing events from the PAR code. What are your thoughts on that? I did it this way since we're trying to emphasize OTEL and de-emphasize our events.

[AndersAbel]

I agree to not introducing new events. Sounds good adding otel metrics once both are merged.

[josephdecock]

We should instrument /connect/par and also we should update the instrumentation in /connect/authorize to tag requests that used par. We can use ValidatedAuthorizeRequest.IsPushedAuthorizationRequest to know in the authorize endpoint if the request was pushed.

[brockallen]

This is now merged: #1456