Debug changes

Web/app.py

@@ -7047,6 +7047,7 @@ def ausleihen(id):
         if current_permissions['actions'].get('can_borrow') and not is_library_item:
             if student_card_id:
                 student_user = us.get_user_by_student_card(student_card_id)
+                app.logger.debug(f"Borrowing on behalf of student card {student_card_id}: found user {student_user}")
                 if not student_user:
                     flash('Keine Schülerin/kein Schüler mit dieser Ausweis-ID gefunden.', 'error')
                     return redirect(url_for('library'))

Web/modules/database/user.py

@@ -594,8 +594,8 @@ def student_card_exists(student_card_id):
         return False
     client = MongoClient(cfg.MONGODB_HOST, cfg.MONGODB_PORT)
     db = _get_tenant_db(client)
-    users = db['users']
+    users = db['student_cards']
-    exists = users.find_one({'StudentCardId': normalized}) is not None
+    exists = users.find_one({'SchülerName': normalized}) is not None
     client.close()
     return exists
 
@@ -607,8 +607,8 @@ def get_user_by_student_card(student_card_id):
         return None
     client = MongoClient(cfg.MONGODB_HOST, cfg.MONGODB_PORT)
     db = _get_tenant_db(client)
-    users = db['users']
+    users = db['student_cards']
-    found_user = users.find_one({'StudentCardId': normalized})
+    found_user = users.find_one({'SchülerName': normalized})
     client.close()
     return found_user