add refresh token logic

pages/api/auth/[...nextauth].ts

@@ -21,7 +21,7 @@ async function refreshAccessToken(token: JWT): Promise<JWT> {
       refresh_token: token.refreshToken as string,
     });
 
-    const response = await fetch(process.env.TOKEN_ENDPOINT!, {
+    const response = await fetch(process.env.NEXTAUTH_TOKEN_ENDPOINT!, {
       method: 'POST',
       headers: {
         'Content-Type': 'application/json',