Error when saving feedback and visit admin page of feedbacks

Problem/Motivation

Message Error: Call to undefined function Drupal\feedbacks\Form\drupal_set_message() in Drupal\feedbacks\Form\AddFeedback->submitForm() (regel 97

Error: Call to undefined function Drupal\feedbacks\Controller\drupal_get_user_timezone() in Drupal\feedbacks\Controller\AdminFeedbackController->content() (regel 63

Steps to reproduce

1. Install the module
2. Add a feedback.You'll get this error Message Error: Call to undefined function Drupal\feedbacks\Form\drupal_set_message() in Drupal\feedbacks\Form\AddFeedback->submitForm()
3. Go to Feedbacks listing page (/admin/content/feedbacks) .You'll get this error in log Error: Call to undefined function Drupal\feedbacks\Controller\drupal_get_user_timezone() in Drupal\feedbacks\Controller\AdminFeedbackController->content()

Proposed resolution

Remaining tasks

User interface changes

API changes

Data model changes