Add NPM mirror hosting to unified mirrors

This patch makes the necessary modifications to host npm packages
on our mirrors. Changes include:

- index.json as a DirectoryIndex
- Rewrite rules for the AFS folder structure
- mod_substitute invocation to correctly reference absolute tarball
  url's described in the index.json files.

Change-Id: I7f7c6caa6af16101cf104f950968f3c6319b8243

modules/openstack_project/templates/mirror.vhost.erb

@@ -42,6 +42,22 @@ NameVirtualHost <%= @vhost_name %>:<%= @port %>
     RewriteCond %{DOCUMENT_ROOT}/wheel/$1/$2/$2$3 -d
     RewriteRule ^/wheel/([^/]+)/([^/])([^/]*)(/.*)?$ /wheel/$1/$2/$2$3$4 [L]
 
+    <Directory <%= @docroot %>/npm/>
+      DirectoryIndex index.json
+
+      # npm's URL's are:
+      # /npm/-/index.json
+      # /npm/a/aabc/index.json
+      # /npm/a/aabc/latest/index.json
+      # /npm/a/aabc/-/aabc-0.0.0.tgz
+      RewriteCond %{REQUEST_URI} ^/npm/([^/])([^/]*)
+      RewriteCond %{DOCUMENT_ROOT}/npm/$1/$1$2 -d
+      RewriteRule ^([^/])([^/]*)(/.*)?$ $1/$1$2$3 [L]
+
+      AddOutputFilterByType SUBSTITUTE application/json
+      Substitute "s/localhost/<%= @srvname %>\/npm/ni"
+    </Directory>
+
     ErrorLog /var/log/<%= scope.lookupvar("httpd::params::apache_name") %>/<%= @name %>_error.log
     LogLevel warn
     CustomLog /var/log/<%= scope.lookupvar("httpd::params::apache_name") %>/<%= @name %>_access.log combined