Deal with dual-stack enabling the upstream server liveness check behavior

Since `localhost` resolves to IPv4 as well as IPv6, it causes
nginx to enable the upstream server rotation.

```
2025/02/22 15:14:06 [error] 21#21: *1 no live upstreams while connecting to upstream, client: 192.168.127.1, server: ${base_url}, request: "GET /codeserver/?folder=/opt/app-root/src HTTP/1.1", upstream: "http://localhost/?folder=/opt/app-root/src", host: "localhost:8888"
```

Author: jiridanek

codeserver/ubi9-python-3.11/nginx/httpconf/http.conf

@@ -37,3 +37,12 @@ map $http_x_forwarded_proto $custom_scheme {
         default $scheme;
         https https;
 }
+
+###############
+# Dual-stack causes nginx to enable the "If a domain name resolves to several addresses, all of them will be used in a round-robin fashion." behavior
+# https://nginx.org/en/docs/http/ngx_http_proxy_module.html#proxy_next_upstream_tries
+###############
+upstream workbench_server {
+    server localhost:8787 max_fails=0;
+}
+###############

codeserver/ubi9-python-3.11/nginx/serverconf/proxy.conf.template

@@ -45,7 +45,7 @@ location = /codeserver {
 
 location /codeserver/ {
     # Standard code-server/NGINX configuration
-    proxy_pass http://localhost:8787/;
+    proxy_pass http://workbench_server/;
     proxy_http_version 1.1;
     proxy_set_header Upgrade $http_upgrade;
     proxy_set_header Connection $connection_upgrade;

codeserver/ubi9-python-3.11/nginx/serverconf/proxy.conf.template_nbprefix

@@ -59,8 +59,9 @@ location = / {
 location /codeserver/ {
     rewrite ^/codeserver/(.*)$ /$1 break;
     # Standard RStudio/NGINX configuration
-    proxy_pass http://localhost:8787;
+    proxy_pass http://workbench_server/;
     proxy_http_version 1.1;
+
     proxy_set_header Upgrade $http_upgrade;
     proxy_set_header Connection $connection_upgrade;
     proxy_read_timeout 20d;

rstudio/c9s-python-3.11/nginx/httpconf/http.conf

@@ -37,3 +37,12 @@ map $http_x_forwarded_proto $custom_scheme {
         default $scheme;
         https https;
 }
+
+###############
+# Dual-stack causes nginx to enable the "If a domain name resolves to several addresses, all of them will be used in a round-robin fashion." behavior
+# https://nginx.org/en/docs/http/ngx_http_proxy_module.html#proxy_next_upstream_tries
+###############
+upstream workbench_server {
+    server localhost:8787 max_fails=0;
+}
+###############

rstudio/c9s-python-3.11/nginx/serverconf/proxy.conf.template

@@ -50,7 +50,7 @@ location = /rstudio {
 location /rstudio/ {
     rewrite ^/rstudio/(.*)$ /$1 break;
     # Standard RStudio/NGINX configuration
-    proxy_pass http://localhost:8787;
+    proxy_pass http://workbench_server/;
     proxy_http_version 1.1;
     proxy_set_header Upgrade $http_upgrade;
     proxy_set_header Connection $connection_upgrade;

rstudio/c9s-python-3.11/nginx/serverconf/proxy.conf.template_nbprefix

@@ -77,7 +77,7 @@ location = / {
 location /rstudio/ {
     rewrite ^/rstudio/(.*)$ /$1 break;
     # Standard RStudio/NGINX configuration
-    proxy_pass http://localhost:8787;
+    proxy_pass http://workbench_server/;
     proxy_http_version 1.1;
     proxy_set_header Upgrade $http_upgrade;
     proxy_set_header Connection $connection_upgrade;