Uploading new course groups while there are in-flight requests breaks queue with 'not found' error

[mterwill]

When new course groups are uploaded, we wipe out any existing groups and create all new ones:

office-hours-help-queue/app/controllers/admin/courses_controller.rb

Lines 58 to 84 in c4eb3ca

	def groups
	if request.method == 'GET'
	@course_group_string = @course.get_group_string
	return
	end
	begin
	ActiveRecord::Base.transaction do
	@course.course_groups.destroy_all
	params[:groups].strip().split("\n").each do |emails_csv|
	emails = emails_csv.strip().split(',')
	next unless emails.any?
	group = @course.course_groups.create!
	emails.map do |email|
	group.students << User.find_or_create_by(email: email.strip())
	end
	end
	end
	redirect_to admin_course_url(@course)
	rescue ActiveRecord::RecordInvalid => err
	@course_group_string = params[:groups]
	@err = err
	render :groups
	end
	end

If this is done mid-semester with active requests, since we denormalize course_group_id onto the request at submit time, any existing course group IDs become invalid. We're not using foreign keys in our schema (I'm not sure why) so this ends up propagating up to a runtime error when we try to resolve groups for open requests: Couldn't find CourseGroup with 'id'.

[mterwill]

ad-hoc fix with

mysql> update course_queue_entries set course_group_id = NULL where course_queue_id = 753 and resolved_at is null;
Query OK, 13 rows affected (0.05 sec)
Rows matched: 13  Changed: 13  Warnings: 0