UI: better calculation for advanced secret in KV v2 (#24513)

* Add util for determining whether secret data is advanced

* Add test coverage for bug

* use non-dumb logic for detecting advanced object

* Add changelog

* Add header

* Move util to core

* Add escaped newline to test coverage

* headers again *eyeroll*

ui/lib/core/addon/utils/advanced-secret.js

@@ -0,0 +1,20 @@
+/**
+ * Copyright (c) HashiCorp, Inc.
+ * SPDX-License-Identifier: MPL-2.0
+ */
+
+/**
+ * Method to check whether the secret value is a nested object (returns true)
+ * All other values return false
+ * @param value string or stringified JSON
+ * @returns boolean
+ */
+export function isAdvancedSecret(value) {
+  try {
+    const json = JSON.parse(value);
+    if (Array.isArray(json)) return false;
+    return Object.values(json).some((value) => typeof value !== 'string');
+  } catch (e) {
+    return false;
+  }
+}