[PM-6404] Add UserKeyDefinition (#8052)

* Add `UserKeyDefinition`

* Fix Deserialization Helpers

* Fix KeyDefinition

* Move `ClearEvent`

* Address PR Feedback

* Feedback

libs/common/src/platform/state/deserialization-helpers.ts

@@ -0,0 +1,38 @@
+import { Jsonify } from "type-fest";
+
+/**
+ *
+ * @param elementDeserializer
+ * @returns
+ */
+export function array<T>(
+  elementDeserializer: (element: Jsonify<T>) => T,
+): (array: Jsonify<T[]>) => T[] {
+  return (array) => {
+    if (array == null) {
+      return null;
+    }
+
+    return array.map((element) => elementDeserializer(element));
+  };
+}
+
+/**
+ *
+ * @param valueDeserializer
+ */
+export function record<T, TKey extends string = string>(
+  valueDeserializer: (value: Jsonify<T>) => T,
+): (record: Jsonify<Record<TKey, T>>) => Record<TKey, T> {
+  return (jsonValue: Jsonify<Record<TKey, T> | null>) => {
+    if (jsonValue == null) {
+      return null;
+    }
+
+    const output: Record<string, T> = {};
+    for (const key in jsonValue) {
+      output[key] = valueDeserializer((jsonValue as Record<string, Jsonify<T>>)[key]);
+    }
+    return output;
+  };
+}