Upload to Intervals

Intervals has a [nice API](https://intervals.icu/api-docs.html#put-/api/v1/athlete/-id-/workouts/-workoutId-) available for uploading workouts to your calendar ([example](https://forum.intervals.icu/t/uploading-planned-workouts-to-intervals-icu/63624)). Theoretically these would also get pushed to Zwift directly, since they're an official training partner?

Would be a neat thing to investigate.