docker image: use /run/acme-challenge for acme challenges

This alias the URL '/.well-known/acme-challenge' in the http frontend to
the path '/run/acme-challenge'.

This allows easy configuration of ssl certificates from letsencrypt
using any acme client which supports the webroot mode.

Note that this change on its own does not do anything without further
action (i.e. installing and configuring an acme client).

haproxy.conf

@@ -41,8 +41,15 @@ backend proxy
 
 frontend http
     bind *:80
+
+    # acme request path (for ssl certificates)
+    acl is_acme path_beg /.well-known/acme-challenge
+
     # permanent redirect to https
-    redirect scheme https code 301
+    redirect scheme https code 301 if !is_acme
+
+    # static serve acme request
+    use_backend static if is_acme
 
 frontend https
     bind *:443 ssl crt /nopassphrase.pem no-sslv3

nginx.conf

@@ -7,5 +7,11 @@ server {
                 rewrite ^/static/(.*) /$1;
                 try_files $uri $uri/ =404;
         }
+
         location / {}  # Needed for access to the index.htm
+
+        # acme request path (for ssl certificates)
+        location /.well-known/acme-challenge {
+                alias /run/acme-challenge;
+        }
 }