How do I add a custom Image to an HKWorkout in Swift?

I am working on a workout App where users can save their workouts to HealthKit. However, when I save the workout, it does not have an image in the Apple Fitness App overview. So my question is, how can I add this? I know that it works, because f.e. Matrix (provider of Gym Equipment) safes the Workouts with their Icon (see below).

The Fitness app and HealthKit use your app icon for the image.

How do I add a custom Image to an HKWorkout in Swift?
 
 
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