Merge branch 'fix-delete-exercises' into v5.0.1

...exercises_and_assignments_add_creation_date/migration.sql

ExpressAPI/prisma/schema.prisma

ExpressAPI/prisma/seed.ts

ExpressAPI/src/managers/ExerciseManager.ts

ExpressAPI/src/managers/GitlabManager.ts

ExpressAPI/src/routes/AssignmentRoutes.ts

ExpressAPI/src/routes/ExerciseRoutes.ts