Phase 1 of migrating APPR-specific tables to tables with the Appr prefix

Fixes https://jira.coreos.com/browse/QUAY-950

util/config/schema.py

@@ -881,6 +881,13 @@ CONFIG_SCHEMA = {
       'x-example': False,
     },
 
+    # Feature Flag: Read only app registry.
+    'FEATURE_READONLY_APP_REGISTRY': {
+      'type': 'boolean',
+      'description': 'Whether to App repositories are read-only. Defaults to False',
+      'x-example': True,
+    },
+
     # Feature Flag: Public Reposiotires in _catalog Endpoint.
     'FEATURE_PUBLIC_CATALOG': {
       'type': 'boolean',