Enable DEFAULT_MODE to be customized in config

- Keeps platform set default of "Audit" to be backwards compatible and not break stuff
- get COURSE_MODE_DEFAULTS from config if set

common/djangoapps/course_modes/models.py

@@ -6,6 +6,7 @@ from datetime import datetime, timedelta
 
 import pytz
 from config_models.models import ConfigurationModel
+from django.conf import settings
 from django.core.exceptions import ValidationError
 from django.db import models
 from django.db.models import Q
@@ -119,8 +120,18 @@ class CourseMode(models.Model):
     NO_ID_PROFESSIONAL_MODE = "no-id-professional"
     CREDIT_MODE = "credit"
 
-    DEFAULT_MODE = Mode(AUDIT, _('Audit'), 0, '', 'usd', None, None, None, None)
-    DEFAULT_MODE_SLUG = AUDIT
+    DEFAULT_MODE = Mode(
+        settings.COURSE_MODE_DEFAULTS['slug'],
+        settings.COURSE_MODE_DEFAULTS['name'],
+        settings.COURSE_MODE_DEFAULTS['min_price'],
+        settings.COURSE_MODE_DEFAULTS['suggested_prices'],
+        settings.COURSE_MODE_DEFAULTS['currency'],
+        settings.COURSE_MODE_DEFAULTS['expiration_datetime'],
+        settings.COURSE_MODE_DEFAULTS['description'],
+        settings.COURSE_MODE_DEFAULTS['sku'],
+        settings.COURSE_MODE_DEFAULTS['bulk_sku'],
+    )
+    DEFAULT_MODE_SLUG = settings.COURSE_MODE_DEFAULTS['slug']
 
     # Modes utilized for audit/free enrollments
     AUDIT_MODES = [AUDIT, HONOR]