Kubernetes Nginx Gateway with Upstreams from ConfigMap

nginx-conf.d-conf-file

include /etc/nginx/conf.d/upstreams/*.conf;

server {
    listen          8080;
    resolver        10.99.254.254;
    server_name     ~^(?<svc>[a-zA-Z0-9]+)(?<env>[\-a-zA-Z0-9]*)\..*\.com$;
    
    location / {
    	proxy_set_header X-Real-IP $remote_addr;
    	proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
    	proxy_set_header Host $http_host;
    	proxy_redirect off;
    	proxy_next_upstream error;

    	# 2) Any request that did not originally come in to the ELB
    	#    over HTTPS gets redirected.
    	if ($http_x_forwarded_proto != "https") {
      		rewrite ^(.*)$ https://$host$1 permanent;
    	}

    	proxy_pass http://$svc;

    	# Add HTTP Strict Transport Security for good measure.
	    add_header Strict-Transport-Security "max-age=31536000; includeSubDomains;";
    }
}

nginx-configmap.yaml

kind: ConfigMap
apiVersion: v1
metadata:
  name: nginx-config
data:
  nginx-upstreams: |
    upstream api {
        server api;
    }
    upstream auth {
        server auth;
    }
    upstream admin {
        server admin;
    }

nginx-deployment.yaml

apiVersion: extensions/v1beta1
kind: Deployment
metadata:
  name: nginx-gateway
  labels:
    name: nginx-gateway
    role: frontend
    application: nginx
spec:
  replicas: 2
  strategy:
    rollingUpdate:
      maxSurge: 2
      maxUnavailable: 1
    type: RollingUpdate
  template:
    metadata:
      labels:
        name: nginx-gateway
        role: frontend
        application: nginx
    spec:
      containers:
      - name: nginx-gateway
        image: __some_account__/nginx-gateway:latest
        ports:
        - containerPort: 80
        volumeMounts:
          - mountPath: /etc/nginx/conf.d/upstreams
            name: nginx-upstreams
      volumes:
      - name: nginx-upstreams
        configMap:
          name: nginx-config
          items:
          - key: nginx-upstreams
            path: upstreams.conf

Hi, I'm looking to add nginx gateway for my api's for GKE cluster that I've already develop. By assumption, I deploy this files as is?
Is there resource of information that details how to do this? Thanks