Add Optional 2FA Support (#61)

* Add TOTP MFA Support

* Add Passkey MFA Support

It's not impossible I missed some minor cleanup, but most things make sense and there isn't a lot of obvious duplication anymore.

---------

Co-authored-by: Bruno Bernardino <me@brunobernardino.com>

routes/api/auth/multi-factor/passkey/begin.ts

@@ -0,0 +1,87 @@
+import { Handlers } from 'fresh/server.ts';
+import { PublicKeyCredentialCreationOptionsJSON } from '@simplewebauthn/server';
+
+import { FreshContextState } from '/lib/types.ts';
+import { PasskeyModel } from '/lib/models/multi-factor-auth/passkey.ts';
+import { UserModel } from '/lib/models/user.ts';
+import { AppConfig } from '/lib/config.ts';
+
+export interface RequestBody {
+  email: string;
+}
+
+export interface ResponseBody {
+  success: boolean;
+  error?: string;
+  options?: PublicKeyCredentialCreationOptionsJSON;
+  sessionData?: {
+    challenge: string;
+    methodId: string;
+  };
+}
+
+export const handler: Handlers<unknown, FreshContextState> = {
+  async POST(request) {
+    const isMultiFactorAuthEnabled = await AppConfig.isMultiFactorAuthEnabled();
+
+    if (!isMultiFactorAuthEnabled) {
+      const responseBody: ResponseBody = {
+        success: false,
+        error: 'Passwordless passkey login requires multi-factor authentication to be enabled.',
+      };
+
+      return new Response(JSON.stringify(responseBody), { status: 403 });
+    }
+
+    const body = await request.clone().json() as RequestBody;
+    const { email } = body;
+
+    if (!email) {
+      const responseBody: ResponseBody = {
+        success: false,
+        error: 'Email is required',
+      };
+
+      return new Response(JSON.stringify(responseBody), { status: 400 });
+    }
+
+    const user = await UserModel.getByEmail(email);
+
+    if (!user) {
+      const responseBody: ResponseBody = {
+        success: false,
+        error: 'User not found',
+      };
+
+      return new Response(JSON.stringify(responseBody), { status: 404 });
+    }
+
+    const config = await AppConfig.getConfig();
+    const allowedCredentials = PasskeyModel.getCredentialsFromUser(user);
+
+    if (allowedCredentials.length === 0) {
+      const responseBody: ResponseBody = {
+        success: false,
+        error: 'No passkeys registered for this user',
+      };
+
+      return new Response(JSON.stringify(responseBody), { status: 400 });
+    }
+
+    const options = await PasskeyModel.generateAuthenticationOptions(
+      config.auth.baseUrl,
+      allowedCredentials,
+    );
+
+    const responseBody: ResponseBody = {
+      success: true,
+      options,
+      sessionData: {
+        challenge: options.challenge,
+        methodId: options.challenge,
+      },
+    };
+
+    return new Response(JSON.stringify(responseBody));
+  },
+};