feat: add functionality for linking teachers to classes with a new UI tab and API endpoint

backend/routes/api.py

@@ -459,6 +459,29 @@ def set_my_classes():
     return jsonify({'my_classes': [{'id': c.id, 'name': c.name} for c in current_user.classes]})
 
 
+
+# ── Klas-leerkracht koppeling (directeur) ──────────────────────────────────────
+
+@api_bp.route('/classes/<int:class_id>/teachers', methods=['PUT'])
+@login_required
+@director_required
+def set_class_teachers(class_id):
+    """Directeur koppelt leerkrachten aan een klas."""
+    klas = Class.query.filter_by(id=class_id, school_id=current_user.school_id).first_or_404()
+    data     = request.get_json() or {}
+    user_ids = data.get('teacher_ids', [])
+    teachers = User.query.filter(
+        User.id.in_(user_ids),
+        User.school_id == current_user.school_id,
+        User.is_active == True,
+    ).all()
+    klas.users = teachers
+    audit_log('class.user_assignment', 'class', target_id=str(class_id),
+              detail={'class_name': klas.name, 'teacher_ids': user_ids,
+                      'teacher_names': [t.full_name for t in teachers]})
+    db.session.commit()
+    return jsonify({'teachers': [{'id': t.id, 'full_name': t.full_name} for t in teachers]})
+
 # ── Auditlog ───────────────────────────────────────────────────────────────────
 
 @api_bp.route('/audit-log')