feat: Implement get saml auth providers API endpoint

packages/backend/src/serializers/index.js

@@ -1,11 +1,13 @@
 import userSerializer from './user.js';
 import roleSerializer from './role.js';
 import permissionSerializer from './permission.js';
+import samlAuthProviderSerializer from './saml-auth-provider.ee.js';
 
 const serializers = {
   User: userSerializer,
   Role: roleSerializer,
   Permission: permissionSerializer,
+  SamlAuthProvider: samlAuthProviderSerializer,
 };
 
 export default serializers;