ExerciseManager => Add function to get all exercises of an assignment

ExpressAPI/src/managers/ExerciseManager.ts

@@ -12,6 +12,15 @@ class ExerciseManager {
                                                 include: include
                                             }) as unknown as Exercise ?? undefined;
     }
+
+    async getFromAssignment(assignmentName: string, include: Prisma.ExerciseInclude | undefined = undefined): Promise<Array<Exercise> | undefined> {
+        return await db.exercise.findMany({
+                                              where  : {
+                                                  assignmentName: assignmentName
+                                              },
+                                              include: include
+                                          }) as Array<Exercise> ?? undefined;
+    }
 }