fix: functies uit submission repo zijn bereikbaar

backend/src/entities/assignments/submission.entity.ts

@@ -2,8 +2,13 @@ import { Student } from '../users/student.entity.js';
 import { Group } from './group.entity.js';
 import { Entity, Enum, ManyToOne, PrimaryKey, Property } from '@mikro-orm/core';
 import { Language } from '../content/language.js';
+import { SubmissionRepository } from '../../data/assignments/submission-repository.js';
 
-@Entity()
+@Entity({
+    repository: () => {
+        return SubmissionRepository;
+    },
+})
 export class Submission {
     @PrimaryKey({ type: 'string' })
     learningObjectHruid!: string;