v3.8.6

Improvements and bugfixes:

• Fix problem with accessing Artemis from online courses over LTI
• Fix download repos for courses with '/' in the name
• Improve the visual quality of interactive UML diagrams
• Improve the C template for programming exercises
• Don't show the trigger button for inactive participations
• Improve consistency of exercise status messages
• Fix health and tracker in server administration
• Fix a type error in the result details component