restructure and reorganize

src/app.d.ts

@@ -5,8 +5,9 @@ declare global {
     // interface Error {}
     interface Locals {
       session?: {
-        accessToken: string;
-        refreshToken: string;
+        accessToken: string | null;
+        refreshToken: string | null;
+        set(accessToken: string, refreshToken: string): Promise<void>;
       };
     }
     // interface PageData {}