Prevent interns from uploading duplicate sets

[mek32390]

Once a class set is approved for a class, another intern shouldn't be able to submit a set to that class. The class should be instructor and section specific. The issue is that on mchp, we don't have sections. Here is an example:

• Intern 1 submits a class set for ECON 100 with instructor Bill, which has 200 students on the roster (the roster was for Section A of the class)
• Intern 2 submits a class set for ECON 100 with instructor Bill, which has another 200 students (the roster was for Section B of the class)

The above situation should be allowed, because although Intern 1 already submitted a class set for ECON 100 with instructor Bill, Intern 1 only submitted it for Section A of the class. There was an additional section, B, that had a new roster associated with it, and had all new students.

So, in order to not allow the submission of duplicate sets for a class, a submitted set can't be for the same course, instructor, AND can't have the same roster as a previously submitted set. But, even though there are two sections and therefore two rosters, on mchp, there is still only one course: ECON 100 with Instr Bill, and that course still only has 1 primary calendar.

[Johnsel]

Almost done with this baby, sadly I got stuck and @mitchellias not around :(

[Johnsel]

mchp/schedule/views.py class CourseRemoveView(_BaseCourseView, AjaxableResponseMixin):