Merge remote-tracking branch 'origin/dev' into fix/class-join-request

# Conflicts:
#	backend/src/controllers/classes.ts
#	backend/src/data/questions/question-repository.ts
#	backend/tests/controllers/students.test.ts
#	backend/tests/controllers/teachers.test.ts

common/src/interfaces/answer.ts

@@ -1,14 +1,19 @@
-import { UserDTO } from './user';
 import { QuestionDTO, QuestionId } from './question';
+import { TeacherDTO } from './teacher';
 
 export interface AnswerDTO {
-    author: UserDTO;
+    author: TeacherDTO;
     toQuestion: QuestionDTO;
     sequenceNumber: number;
     timestamp: string;
     content: string;
 }
 
+export interface AnswerData {
+    author: string;
+    content: string;
+}
+
 export interface AnswerId {
     author: string;
     toQuestion: QuestionId;

common/src/interfaces/learning-content.ts

@@ -11,7 +11,7 @@ export interface Transition {
     };
 }
 
-export interface LearningObjectIdentifier {
+export interface LearningObjectIdentifierDTO {
     hruid: string;
     language: Language;
     version?: number;

common/src/interfaces/question.ts

@@ -1,15 +1,20 @@
-import { LearningObjectIdentifier } from './learning-content';
+import { LearningObjectIdentifierDTO } from './learning-content';
 import { StudentDTO } from './student';
 
 export interface QuestionDTO {
-    learningObjectIdentifier: LearningObjectIdentifier;
+    learningObjectIdentifier: LearningObjectIdentifierDTO;
     sequenceNumber?: number;
     author: StudentDTO;
-    timestamp?: string;
+    timestamp: string;
+    content: string;
+}
+
+export interface QuestionData {
+    author?: string;
     content: string;
 }
 
 export interface QuestionId {
-    learningObjectIdentifier: LearningObjectIdentifier;
+    learningObjectIdentifier: LearningObjectIdentifierDTO;
     sequenceNumber: number;
 }

common/src/interfaces/submission.ts

@@ -1,10 +1,10 @@
 import { GroupDTO } from './group';
-import { LearningObjectIdentifier } from './learning-content';
+import { LearningObjectIdentifierDTO } from './learning-content';
 import { StudentDTO } from './student';
 import { Language } from '../util/language';
 
 export interface SubmissionDTO {
-    learningObjectIdentifier: LearningObjectIdentifier;
+    learningObjectIdentifier: LearningObjectIdentifierDTO;
 
     submissionNumber?: number;
     submitter: StudentDTO;