Como usar um nginx.conf personalizado no GKE

http {
  include /etc/nginx/mime.types;
  server_tokens off;
  client_max_body_size 32m;

  upstream app_server {
    server localhost:8081;
    keepalive 128;
  }

  endpoints {
    metadata_server;
  }

  server {
    # Running port
    listen 8080;

    # Running ssl port
    listen 443 ssl;
    ssl_certificate /etc/nginx/ssl/nginx.crt;
    ssl_certificate_key /etc/nginx/ssl/nginx.key;

    # Logging to stdout enables better integration with Docker and GKE/Kubernetes.
    access_log /dev/stdout;

    location / {
      # Begin Endpoints v2 Support
      endpoints {
        on;
        # After ESP 1.7.0, "server_config" field is required.
        # It has to be /etc/nginx/server_config.pb.txt exactly.
        # If not present, some new features will not work.
        server_config /etc/nginx/server_config.pb.txt;

        # After ESP 1.7.0, "api" field is not required.
        # If added, it has to be /etc/nginx/endpoints/service.json exactly.
        # api /etc/nginx/endpoints/service.json;

        # Uncomment the line below if you are not using Google Container Engine.
        # The path should be set to the “-k” path specified in the ESP container’s                 
        # args section in the Kubernetes yaml config.
        # google_authentication_secret /etc/nginx/creds/service-account-creds.json;
      }
      # End Endpoints v2 Support

      proxy_pass http://app_server;
      proxy_redirect off;
      proxy_set_header Host $host;
      proxy_set_header X-Real-IP $remote_addr;
      proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
      proxy_set_header X-Forwarded-Host $server_name;
      proxy_set_header X-Google-Real-IP $remote_addr;

      # 86400 seconds (24 hours) is the maximum a server is allowed.
      proxy_send_timeout 86400s;
      proxy_read_timeout 86400s;
    }

    include /var/lib/nginx/extra/*.conf;
  }

  server {
    # expose /nginx_status but on a different port to avoid
    # external visibility / conflicts with the app.
    listen 8090;
    location /nginx_status {
      stub_status on;
      access_log off;
    }
    location / {
      root /dev/null;
    }
  }
}

template:
  metadata:
    labels:
      app: esp-echo
  spec:
    volumes:
    - name: nginx-config
      configMap:
        name: nginx-config
    - name: nginx-ssl
      secret:
        secretName: nginx-ssl
    containers:
    - name: esp
      image: gcr.io/endpoints-release/endpoints-runtime:1
      args: [
        "-n", "/etc/nginx/custom/nginx.conf",
        "-s", "SERVICE_NAME",
        "--rollout_strategy", "managed",
      ]
      ports:
        - containerPort: 8080
        - containerPort: 443
      volumeMounts:
      - mountPath: /etc/nginx/ssl
        name: nginx-ssl
        readOnly: true
      - mountPath: /etc/nginx/custom
        name: nginx-config
        readOnly: true
    - name: echo 
      image: gcr.io/endpoints-release/echo:latest
      ports:
        - containerPort: 8081