Add a course setting for limiting access to course instance to LTI only

[oseppala]

In case students use A-plus material through LTI from MyCourses it is crucial that they don't access the course directly from A-plus. In such a case the points from exercises are not transferred to MyCourses Gradebook.

The suggested change is to add a setting alongside "visible to students", "visible to students via LTI only"

The setting would deny a logged in student user from accessing the course if the login is not through LTI.

note: The student might have an open session in A-plus while they access the course via MyCourses.

[oseppala]

@janmikaelr can provide more details.

[janmikaelr]

This feature affects multiple Language Centre English courses and a ELEC master’s thesis seminar course.

[oseppala]

Possible duplicate of #1296