restrict duplicate enrollment only if user is verified (#2199)

* restrict duplicate enrollment only if user is verified

* more

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

---------

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

courses/views/v1/__init__.py

@@ -74,6 +74,7 @@
     sync_enrollments_with_edx,
     unsubscribe_from_edx_course_emails,
 )
+from openedx.constants import EDX_ENROLLMENT_VERIFIED_MODE
 from openedx.exceptions import (
     EdxApiEmailSettingsErrorException,
     NoEdxApiAuthError,
@@ -252,7 +253,10 @@ def _validate_enrollment_post_request(
     if (
         PaidCourseRun.fulfilled_paid_course_run_exists(user, run)
         or CourseRunEnrollment.objects.filter(
-            user=user, run=run, change_status=None
+            user=user,
+            run=run,
+            change_status=None,
+            enrollment_mode=EDX_ENROLLMENT_VERIFIED_MODE,
         ).exists()
     ):
         resp = redirect_with_user_message(