chore: Improve typings around model methods (#6324)

app/types.ts

@@ -1,5 +1,7 @@
+/* eslint-disable @typescript-eslint/ban-types */
 import { Location, LocationDescriptor } from "history";
 import { TFunction } from "i18next";
+import { JSONValue } from "@shared/types";
 import RootStore from "~/stores/RootStore";
 import Document from "./models/Document";
 import FileOperation from "./models/FileOperation";
@@ -198,3 +200,10 @@ export type WebsocketEvent =
 export type AwarenessChangeEvent = {
   states: { user?: { id: string }; cursor: any; scrollY: number | undefined }[];
 };
+
+// TODO: Can we make this type driven by the @Field decorator
+export type Properties<C> = {
+  [Property in keyof C as C[Property] extends JSONValue
+    ? Property
+    : never]?: C[Property];
+};