How to solve FastApi Keycloak token url resolved from DNS to Docker Container Name?

i'm trying to set up an auth flow in my FastApi service. I have a working docker container for Keycloak, FastApi and Nginx. In nginx i redirect the connection to server's ip, to both keycloak and fastapi (i have 2 domains, lets call them keycloakdomain.com and fastapidomain.com).

I'm using the FastApiKeycloak library to authenticate in Keycloak. I want to authorize via the "Authorize" button, in the swagger docs of my fastapi service so i can get the access token for subsequent requests, from my keycloak instance.

Here's my configuration code in FastApi:

keycloak = FastAPIKeycloak(
   server_url="https://keycloakdomain.com/auth",
   client_id="mykeycloakclient",
   client_secret="secret",
   admin_client_secret="secret",
   realm="realmname",
   callback_uri="https://fastapidomain.com/docs",
 )
 keycloak.add_swagger_config(app)

Then i protect an endpoint so the Authorize button is shown. When i click on it, here's what i see:

In the TOKEN URL i have the container name and port, not the url domain that i wrote in the configuration object (the protocol is HTTP, not HTTPS).

I'm expecting to see "https://keycloakdomain.com/auth/realms ...".

Am I doing something wrong here? Can i set the baseUrl somewhere?

P.S:
If I make a POST request with postman to the endpoint im expecting (the one with domain name), i get the access token and the data i actually need.

I found a solution to the problem. The issue was with the nginx configuration of Keycloak. I didn't set the headers and so the reverse proxy wasn't forwarding host headers properly.

See this answer from Jan: https://stackoverflow.com/questions/66176321/keycloak-behind-reverse-proxy-mixes-internal-and-external-addresses

Hope this could help someone else.