Merge branch 'feat/service-layer' into feat/service-layer-adriaan

# Conflicts:
#	backend/src/controllers/classes.ts
#	backend/src/controllers/students.ts
#	backend/src/data/users/teacher-repository.ts
#	backend/src/interfaces/assignment.ts
#	backend/src/interfaces/teacher.ts
#	backend/src/routes/classes.ts
#	backend/src/services/assignments.ts
#	backend/src/services/class.ts
#	backend/src/services/students.ts
#	backend/src/util/translation-helper.ts

backend/src/interfaces/student.ts

@@ -0,0 +1,32 @@
+import { Student } from "../entities/users/student.entity.js";
+
+export interface StudentDTO {
+    id: string;
+    username: string;
+    firstName: string;
+    lastName: string;
+    endpoints?: {
+        classes: string;
+        questions: string;
+        invitations: string;
+        groups: string;
+    };
+}
+
+export function mapToStudentDTO(student: Student): StudentDTO {
+    return {
+        id: student.username,
+        username: student.username,
+        firstName: student.firstName,
+        lastName: student.lastName,
+    };
+}
+
+export function mapToStudent(studentData: StudentDTO): Student {
+    const student = new Student();
+    student.username = studentData.username;
+    student.firstName = studentData.firstName;
+    student.lastName = studentData.lastName;
+
+    return student;
+}