fix: adjust discussions app APIs to match consuming frontend (#27085)

This commit adjusts a few values in our discussions configuration APIs to make them match what the frontend needs, as well as to more accurately reflect the providers available today.

- The `active` provider ID is expressed as None if it doesn’t exist
- The “cs_comments_service” provider has been renamed “legacy” - when we implement the new discussions micro-frontend, we’ll also have a separate provider for that, so they can’t both be “cs_comments_service”.  Also, cs_comments_service is such a bad name for anything.
- The hard-coded providers list in get_supported_providers now includes ‘legacy’ and ‘piazza’, our two known providers.  This list will be updated as more known providers come online.
- The PROVIDER_FEATURE_MAP has similarly been updated.

Part of this task: TNL-8093

openedx/core/djangoapps/discussions/migrations/0003_alter_provider_filter_list.py

+# Generated by Django 2.2.19 on 2021-03-23 14:46
+
+from django.db import migrations, models
+import django_mysql.models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('discussions', '0002_add_provider_filter'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='providerfilter',
+            name='allow',
+            field=django_mysql.models.ListCharField(models.CharField(choices=[('legacy', 'legacy'), ('piazza', 'piazza')], max_length=20), blank=True, help_text='Comma-separated list of providers to allow, eg: legacy,piazza', max_length=63, size=3, verbose_name='Allow List'),
+        ),
+        migrations.AlterField(
+            model_name='providerfilter',
+            name='deny',
+            field=django_mysql.models.ListCharField(models.CharField(choices=[('legacy', 'legacy'), ('piazza', 'piazza')], max_length=20), blank=True, help_text='Comma-separated list of providers to deny, eg: legacy,piazza', max_length=63, size=3, verbose_name='Deny List'),
+        ),
+    ]

openedx/core/djangoapps/discussions/models.py

@@ -29,9 +29,8 @@ def get_supported_providers() -> list[str]:
     TODO: Load this from entry points?
     """
     providers = [
-        'cs_comments_service',
-        'lti',
-        'test',
+        'legacy',
+        'piazza',
     ]
     return providers
 

openedx/core/djangoapps/discussions/tests/test_models.py

@@ -13,9 +13,8 @@ from ..models import DiscussionsConfiguration
 from ..models import ProviderFilter
 
 SUPPORTED_PROVIDERS = [
-    'cs_comments_service',
-    'lti',
-    'test',
+    'legacy',
+    'piazza',
 ]
 
 
@@ -137,7 +136,7 @@ class DiscussionsConfigurationModelTest(TestCase):
         self.configuration_with_values = DiscussionsConfiguration(
             context_key=self.course_key_with_values,
             enabled=False,
-            provider_type='cs_comments_service',
+            provider_type='legacy',
             plugin_configuration={
                 'url': 'http://localhost',
             },
@@ -186,14 +185,14 @@ class DiscussionsConfigurationModelTest(TestCase):
         configuration.plugin_configuration = {
             'url': 'http://localhost',
         }
-        configuration.provider_type = 'cs_comments_service'
+        configuration.provider_type = 'legacy'
         configuration.save()
         configuration = DiscussionsConfiguration.objects.get(context_key=self.course_key_with_defaults)
         assert configuration is not None
         assert not configuration.enabled
         assert configuration.lti_configuration is None
         assert configuration.plugin_configuration['url'] == 'http://localhost'
-        assert configuration.provider_type == 'cs_comments_service'
+        assert configuration.provider_type == 'legacy'
 
     def test_is_enabled_nonexistent(self):
         """
@@ -247,4 +246,4 @@ class DiscussionsConfigurationModelTest(TestCase):
         assert not configuration.enabled
         assert not configuration.lti_configuration
         assert configuration.plugin_configuration
-        assert configuration.provider_type == 'cs_comments_service'
+        assert configuration.provider_type == 'legacy'

openedx/core/djangoapps/discussions/views.py

@@ -14,10 +14,9 @@ from .models import DiscussionsConfiguration
 
 
 PROVIDER_FEATURE_MAP = {
-    'cs_comments_service': [
+    'legacy': [
         'discussion-page',
         'embedded-course-sections',
-        'lti',
         'wcag-2.1',
     ],
     'piazza': [
@@ -66,7 +65,7 @@ class DiscussionsConfigurationView(APIView):
                 },
                 'plugin_configuration': instance.plugin_configuration,
                 'providers': {
-                    'active': instance.provider_type or '',
+                    'active': instance.provider_type or None,
                     'available': {
                         provider: {
                             'features': PROVIDER_FEATURE_MAP.get(provider) or [],