refactor: improve quiz retrieval logic with schedule validation

- Added validation to ensure 'scheduleId' is provided when retrieving quizzes, enhancing error handling.
- Implemented a check for the existence of the schedule before proceeding with quiz retrieval, improving robustness.
- Reformatted code for better readability and consistency in the Quiz schema.

src/Quiz/quiz.schema.ts

@@ -211,6 +211,13 @@ export class QuizSchema extends PothosSchema {
             if (!centerMentor) {
               throw new Error('Center mentor not found')
             }
+            if (args.scheduleId) {
+              const schedule = await this.prisma.schedule.findUnique({
+                where: { id: args.scheduleId },
+              })
+              if (!schedule) {
+                throw new Error('Schedule not found')
+              }
               return await this.prisma.quiz.findMany({
                 ...query,
                 where: {
@@ -219,6 +226,8 @@ export class QuizSchema extends PothosSchema {
                 },
               })
             }
+            throw new Error('Schedule ID is required')
+          }
         },
       }),
     }))