feat: Implement get role mappings API endpoint

packages/backend/src/controllers/api/v1/admin/saml-auth-providers/get-role-mappings.ee.js

@@ -0,0 +1,14 @@
+import { renderObject } from '../../../../../helpers/renderer.js';
+import SamlAuthProvider from '../../../../../models/saml-auth-provider.ee.js';
+
+export default async (request, response) => {
+  const samlAuthProvider = await SamlAuthProvider.query()
+    .findById(request.params.samlAuthProviderId)
+    .throwIfNotFound();
+
+  const roleMappings = await samlAuthProvider
+    .$relatedQuery('samlAuthProvidersRoleMappings')
+    .orderBy('remote_role_name', 'asc');
+
+  renderObject(response, roleMappings);
+};