fix: course enrollment admin popup search course

The course enrollment create django admin screen with a popup search
course. That make it more easy to search and find the correct course.
GN-1234

nau_openedx_extensions/student/admin.py

@@ -71,7 +71,7 @@ class NAUCourseEnrollmentAdmin(DisableEnrollmentAdminMixin, admin.ModelAdmin):
     """
     list_display = ('id', 'user', 'email', 'course_id', 'mode', 'is_active',)
     list_filter = ('mode', 'is_active',)
-    raw_id_fields = ('user',)
+    raw_id_fields = ('user', 'course')
     search_fields = ('user__username', 'user__email')
     form = CourseEnrollmentForm
     search_help_text = "Search by user username or email"