feat: add shared UI package auth DI (#5720)

* feat: add shared UI package auth DI

* use refs instead of reactive

* pnpm prepr

* move app auth provider setup to src/providers/setup

apps/frontend/src/providers/setup.ts

@@ -1,6 +1,7 @@
 import { provideNotificationManager } from '@modrinth/ui'
 
 import { FrontendNotificationManager } from './frontend-notifications'
+import { setupAuthProvider } from './setup/auth'
 import { setupFilePickerProvider } from './setup/file-picker'
 import { setupModrinthClientProvider } from './setup/modrinth-client'
 import { setupPageContextProvider } from './setup/page-context'
@@ -9,6 +10,7 @@ import { setupTagsProvider } from './setup/tags'
 export function setupProviders(auth: Awaited<ReturnType<typeof useAuth>>) {
 	provideNotificationManager(new FrontendNotificationManager())
 
+	setupAuthProvider(auth)
 	setupModrinthClientProvider(auth)
 	setupTagsProvider()
 	setupFilePickerProvider()

apps/frontend/src/providers/setup/auth.ts

@@ -0,0 +1,29 @@
+import type { Labrinth } from '@modrinth/api-client'
+import { type AuthProvider, provideAuth } from '@modrinth/ui'
+import { ref, watchEffect } from 'vue'
+
+export function setupAuthProvider(auth: Awaited<ReturnType<typeof useAuth>>) {
+	const router = useRouter()
+	const sessionToken = ref<string | null>(null)
+	const user = ref<Labrinth.Users.v2.User | null>(null)
+
+	const authProvider: AuthProvider = {
+		session_token: sessionToken,
+		user,
+		requestSignIn: async (redirectPath: string) => {
+			await router.push({
+				path: '/auth/sign-in',
+				query: {
+					redirect: redirectPath,
+				},
+			})
+		},
+	}
+
+	watchEffect(() => {
+		sessionToken.value = auth.value.token || null
+		user.value = (auth.value.user as Labrinth.Users.v2.User | null) ?? null
+	})
+
+	provideAuth(authProvider)
+}