Capture and store last seen user flags from the booru

Main use case for these flags is to notify when something they're trying
to use will not be usable due to authorization or their role on the
site. Specifically, it will be also used later to detect when user
is a part of staff and show them staff-specific features.

src/content/user-details.ts

@@ -0,0 +1,14 @@
+import { UserDetails } from "$lib/extension/preferences/UserDetails";
+
+(async () => {
+  const userDetails = new UserDetails();
+  const userDataStore = document.querySelector<HTMLElement>('.js-datastore');
+
+  if (!userDataStore) {
+    return;
+  }
+
+  await userDetails.isAuthorized.set(userDataStore.dataset.userIsSignedIn === 'true');
+})();
+
+

src/lib/extension/preferences/UserDetails.ts

@@ -0,0 +1,16 @@
+import CacheablePreferences, { PreferenceField, type WithFields } from "$lib/extension/base/CacheablePreferences";
+
+export interface UserDetailsFields {
+  isAuthorized: boolean;
+}
+
+export class UserDetails extends CacheablePreferences<UserDetailsFields> implements WithFields<UserDetailsFields> {
+  constructor() {
+    super('userDetails');
+  }
+
+  isAuthorized = new PreferenceField(this, {
+    field: 'isAuthorized',
+    defaultValue: false,
+  });
+}

src/stores/preferences/user.ts

@@ -0,0 +1,18 @@
+import { UserDetails, type UserDetailsFields } from "$lib/extension/preferences/UserDetails";
+import { readable } from "svelte/store";
+
+const userDetails = new UserDetails();
+
+export const user = readable<UserDetailsFields | null>(null, set => {
+  userDetails.subscribe(settings => {
+    set({
+      isAuthorized: Boolean(settings.isAuthorized)
+    });
+  });
+
+  userDetails.isAuthorized.get().then(isAuthorized => {
+    set({
+      isAuthorized
+    });
+  });
+});