Merge remote-tracking branch 'origin/refactor/common' into feat/user-routes

# Conflicts:
#	backend/src/controllers/students.ts
#	backend/src/controllers/teachers.ts
#	backend/src/interfaces/question.ts
#	backend/src/services/classes.ts
#	backend/src/services/students.ts
#	backend/src/services/teachers.ts

common/src/interfaces/answer.ts

@@ -1,5 +1,5 @@
 import { UserDTO } from './user';
-import { QuestionDTO } from './question';
+import { QuestionDTO, QuestionId } from './question';
 
 export interface AnswerDTO {
     author: UserDTO;

common/src/interfaces/group.ts

@@ -1,4 +1,5 @@
 import { AssignmentDTO } from './assignment';
+import { StudentDTO } from './student';
 
 export interface GroupDTO {
     assignment: number | AssignmentDTO;

common/src/interfaces/learning-content.ts

@@ -1,4 +1,4 @@
-import { Language } from 'dwengo-1-backend/src/entities/content/language.js';
+import { Language } from "../util/language";
 
 export interface Transition {
     default: boolean;

common/src/interfaces/question.ts

@@ -1,3 +1,4 @@
+import { LearningObjectIdentifier } from './learning-content';
 import { StudentDTO } from './student';
 
 export interface QuestionDTO {

common/src/interfaces/submission.ts

@@ -1,4 +1,7 @@
 import { GroupDTO } from './group';
+import { LearningObjectIdentifier } from './learning-content';
+import { StudentDTO } from './student';
+import { Language } from '../util/language';
 
 export interface SubmissionDTO {
     learningObjectIdentifier: LearningObjectIdentifier;