feat: Supports custom headers via file /etc/nginx/.env

Remove the print of headers for security

examples/proxy-headers/README.md

@@ -2,20 +2,17 @@
 
 The interface and the docker registry will be accessible with <http://localhost>.
 
-This example highlight the usage of custom headers when the UI is used as a proxy. When you wants to use a header name with hyphens, replace them by underscores in the variable.
+This example highlight the usage of custom headers when the UI is used as a proxy. When you wants to use a header name with hyphens, replace them by underscores in the variable. You can put headers in environment variable or in config file `/etc/nginx/.env`. They have the same writing style.
 
 Headers can be useful in some cases such as avoid sending credentials when you are on the UI. Or give to the registry server other properties such as X-Forward-For header.
 
-I will set these two headers in this example.
+I will set these two headers in this example. X-Forward-For by environment variable and Authorization by file.
 
 In order to set your credentials in the header, you need to know how [Authorization](https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Authorization) header works. Here we use the `Basic` authentication scheme, the credentials are constructed like this:
 - The username and the password are combined with a colon (`registry:ui`).
 - The resulting string is base64 encoded (`cmVnaXN0cnk6dWk=`). You can simply run `echo -n "registry:ui" | base64`.
 - In your header, put this value `Basic cmVnaXN0cnk6dWk=`
-- In your docker-compose, the environment will look like `NGINX_PROXY_HEADER_Authorization=Basic cmVnaXN0cnk6dWk=`
-
-Tip: Use [docker-compose .env file](https://docs.docker.com/compose/environment-variables/#the-env-file) for this .
-
+- In your `/etc/nginx/.env`, the file will contains `NGINX_PROXY_HEADER_Authorization=Basic cmVnaXN0cnk6dWk=`
 
 For X-Forward-For, replace all hyphens by underscores, and the value will be a nginx variable which is `$proxy_add_x_forwarded_for`. In your docker compose you will need to duplicate the `$` character. In your docker-compose, your environment will look like `NGINX_PROXY_HEADER_X_Forwarded_For=$$proxy_add_x_forwarded_for`
 

examples/proxy-headers/docker-compose.yml

@@ -16,8 +16,9 @@ services:
     environment:
       - REGISTRY_TITLE=My Private Docker Registry
       - REGISTRY_URL=http://registry:5000
-      - NGINX_PROXY_HEADER_Authorization=Basic cmVnaXN0cnk6dWk=
       - NGINX_PROXY_HEADER_X_Forwarded_For=$$proxy_add_x_forwarded_for
+    volumes:
+      - ./nginx.env:/etc/nginx/.env
     depends_on:
       - registry
     networks:

examples/proxy-headers/nginx.env

@@ -0,0 +1 @@
+NGINX_PROXY_HEADER_Authorization=Basic cmVnaXN0cnk6dWk=