Coordinators adding users that don't exist

[smartspot2]

In the coordinator view of a section, when attempting to add a student that does not exist (i.e. the user has not logged in to scheduler ever before), the backend errors on a query for the user associated on the email, giving a 500 server error, specifically when running the following line:

csm_web/csm_web/scheduler/views/section.py

Lines 323 to 324 in 8716c11

	# check if the user can actually enroll in the section
	student_user = User.objects.get(email=email)

The expected behavior is to create this user automatically in the backend, though this model creation should not happen if any other errors are present. This means that a small fix changing .get to .get_or_create is not optimal; we'd need to modify the flow slightly to incorporate this case into the feedback loop. This also means that the frontend would likely need to be modified, to display this case in the modal in the situation where other errors occur.

[smartspot2]

#284 has a temporary fix to this, changing the .get to a .get_or_create; this should be changed over when this issue is resolved.