MICROBA-1055 Require a valid enrollment mode, even on the allowlist (#27012)

common/djangoapps/course_modes/api.py

@@ -15,3 +15,15 @@ def get_paid_modes_for_course(course_run_id):
         A list of paid modes (strings) that the course has attached to it.
     """
     return _CourseMode.paid_modes_for_course(course_run_id)
+
+
+def is_eligible_for_certificate(mode_slug, status=None):
+    """
+    Returns whether or not the given mode_slug is eligible for a
+    certificate. Currently all modes other than 'audit' grant a
+    certificate. Note that audit enrollments which existed prior
+    to December 2015 *were* given certificates, so there will be
+    GeneratedCertificate records with mode='audit' which are
+    eligible.
+    """
+    return _CourseMode.is_eligible_for_certificate(mode_slug, status)