Add sign in function

lib/next-auth.d.ts

@@ -0,0 +1,25 @@
+import NextAuth from "next-auth";
+
+declare module "next-auth" {
+  interface Session {
+    refresh_token: string;
+    access_token: string;
+    expires_in: Date;
+  }
+
+  interface User {
+    refresh_token: string;
+    access_token: string;
+    expires_in: Date;
+  }
+}
+
+import { JWT } from "next-auth/jwt";
+
+declare module "next-auth/jwt" {
+  interface JWT {
+    refresh_token: string;
+    access_token: string;
+    expires_in: Date;
+  }
+}