The goal is to add a behat test to verify a teacher can choose to receive notification of assignment submissions

QA test to be automated: MDLQA-67

QA testing instructions

This test requires a teacher account with assignment notifications (via user menu > Preferences > Notification preferences) enabled for web.

1. Log in as a teacher and create an assignment with 'Notify graders about submissions' set to yes, 'Online text' set to yes and 'File submissions' set to no.
2. Log in as a student and submit some text for the assignment.
3. Log in as the teacher and check that you receive a message about the assignment submission.
4. Log in as the student and edit the assignment submission.
5. Log in as the teacher and check that you receive a message about the assignment submission update.