NGINX proxy_pass background request

Hi,

i have the following problem. I have two Applikations each of them have authentication module so when i wants to login the authentication module verfify my data but for each Applikation the authentication module have a different ip.

I need an idea how i can solve this, because the path that the Applikation opens in the backgrounds is the same on both applications

Maybe this example explains it better

location /app1 {
proxy_pass http://IP1:8000;
}

https://IP1/app1 when i login the app opens the background request with https://IP1/auth

location /auth {
internal
proxy_pass http://IP1:8001;
}

location /app2 {
proxy_pass http://IP2:8000;
}

https://IP1/app1 when i login the app opens the background request with https://IP2/auth

location /auth {
internal;
proxy_pass http://IP2:8001;
}


Is this possible without changing the application so that both application can start a request to /auth on different ip addresses?