fix: Run course discussion settings update task when settings change (#30520)

When discussion settings change in a course, call the discussion settings update task so that topics are updated automatically.

openedx/core/djangoapps/discussions/serializers.py

@@ -5,11 +5,12 @@ from django.core.exceptions import ValidationError
 from lti_consumer.api import get_lti_pii_sharing_state_for_course
 from lti_consumer.models import LtiConfiguration
 from rest_framework import serializers
+from xmodule.modulestore.django import modulestore
 
 from lms.djangoapps.discussion.toggles import ENABLE_REPORTED_CONTENT_EMAIL_NOTIFICATIONS
+from openedx.core.djangoapps.discussions.tasks import update_discussions_settings_from_course_task
 from openedx.core.djangoapps.django_comment_common.models import CourseDiscussionSettings
 from openedx.core.lib.courses import get_course_by_id
-from xmodule.modulestore.django import modulestore  # lint-amnesty, pylint: disable=wrong-import-order
 from .models import DiscussionsConfiguration, Provider
 from .utils import available_division_schemes, get_divided_discussions
 
@@ -257,6 +258,7 @@ class DiscussionsConfigurationSerializer(serializers.ModelSerializer):
         # have already been set
         instance = self._update_lti(instance, validated_data)
         instance.save()
+        update_discussions_settings_from_course_task.delay(str(instance.context_key))
         return instance
 
     def _update_lti(