feat: implement tenant OAuth flow and guest achievements

resources/js/admin/auth/pkce.ts

@@ -0,0 +1,16 @@
+import { base64UrlEncode } from './utils';
+
+export function generateState(): string {
+  return base64UrlEncode(window.crypto.getRandomValues(new Uint8Array(32)));
+}
+
+export function generateCodeVerifier(): string {
+  // RFC 7636 recommends a length between 43 and 128 characters.
+  return base64UrlEncode(window.crypto.getRandomValues(new Uint8Array(64)));
+}
+
+export async function generateCodeChallenge(verifier: string): Promise<string> {
+  const data = new TextEncoder().encode(verifier);
+  const digest = await window.crypto.subtle.digest('SHA-256', data);
+  return base64UrlEncode(new Uint8Array(digest));
+}