0.3.0-beta2: don't leak Authorization header from the registry to the redirected destination during @handle_redirects

nginx.conf

@@ -240,6 +240,12 @@ echo "Docker configured with HTTPS_PROXY=$scheme://$http_host/"
             set $original_uri $uri;
             set $orig_loc $upstream_http_location;
 
+            # during this process, nginx will preserve the headers intended for the original destination.
+            # in most cases thats okay, but for some (eg: google storage), passing an Authorization
+            # header can cause problems. Also, that would leak the credentials for the registry
+            # into the storage system (unrelated).
+            proxy_set_header      Authorization "";
+
             # nginx goes to fetch the value from the upstream Location header
             proxy_pass $orig_loc;
             proxy_cache cache;