feat: initial implementation (#2409)

src/core/common/types.ts

@@ -20,6 +20,18 @@ export type Writeable<T> = { -readonly [P in keyof T]: T[P] };
  */
 export type Promiseable<T> = Promise<T> | T;
 
+export type Nullable<T> = { [P in keyof T]: T[P] | null };
+
+export type DeepNullable<T> = T extends object
+  ? {
+      [P in keyof T]: T[P] extends Array<infer U>
+        ? Array<DeepNullable<U>>
+        : T[P] extends ReadonlyArray<infer V>
+        ? ReadonlyArray<DeepNullable<V>>
+        : DeepNullable<T[P]>
+    }
+  : T | null;
+
 /**
  * Like Partial, but recurses down the object marking each field as Partial.
  */