Mandatory lecturer assignment at course creation
It should be mandatory when creating a course to assign at least 1 lecturer. Also, removing the last lecturer of a course should not be supported and an API test for that should be added, similarly like the deleteLastInstructor
test:
https://gitlab.com/tms-elte/backend-core/-/blob/d4c071ef916196d7aac079c9e432ca6061020d9a/tests/api/InstructorGroupsInstructorsCest.php#L135-151