chore: add support for environment specific nginx configuration

This allows for example CSP headers to be defined in a pipeline on a
per-environment basis.

Ref HP-2363

.prod/nginx.conf

@@ -1,4 +1,4 @@
-pid        /tmp/nginx.pid; #for running as non-root 
+pid        /tmp/nginx.pid; #for running as non-root
 
 events {
     worker_connections  4096;  ## Default: 1024
@@ -10,10 +10,10 @@ http {
     fastcgi_temp_path     /tmp/fastcgi_temp;
     uwsgi_temp_path       /tmp/uwsgi_temp;
     scgi_temp_path        /tmp/scgi_temp;
-    
+
     include /etc/nginx/mime.types;
     default_type application/octet-stream;
-    
+
     server {
         listen       8080;
         server_name  localhost;
@@ -29,11 +29,12 @@ http {
         location / {
             root   /usr/share/nginx/html;
             try_files $uri /index.html;
+            include /etc/nginx/env/nginx_env.conf;
         }
 
         error_page   500 502 503 504  /50x.html;
         location = /50x.html {
             root   /usr/share/nginx/html;
         }
-    }        
+    }
 }

.prod/nginx_env.conf

@@ -0,0 +1,2 @@
+# This is a placeholder file for additional environment configuration
+# Actual content is defined by pipeline.

Dockerfile

@@ -71,6 +71,8 @@ COPY --from=staticbuilder /app/build /usr/share/nginx/html
 
 # Copy nginx config
 COPY .prod/nginx.conf  /etc/nginx/
+RUN mkdir /etc/nginx/env
+COPY .prod/nginx_env.conf  /etc/nginx/env
 
 # Copy default environment config and setup script
 # Copy package.json so env.sh can read it