Changes to endpoints so they allow to only get context and then the exercises as well as tidying up a bit

app/services/abc/exam/__init__.py

@@ -4,6 +4,7 @@ from .writing import IWritingService
 from .speaking import ISpeakingService
 from .reading import IReadingService
 from .grade import IGradeService
+from .exercises import IExerciseService
 
 __all__ = [
     "ILevelService",
@@ -12,4 +13,5 @@ __all__ = [
     "ISpeakingService",
     "IReadingService",
     "IGradeService",
+    "IExerciseService"
 ]