Support proxy domain validation for Garage web domains

Also rename the data bag item

site-cookbooks/kosmos_garage/recipes/nginx_web.rb

@@ -3,6 +3,8 @@
 # Recipe:: nginx_web
 #
 
+gandi_api_credentials = data_bag_item('credentials', 'gandi_api')
+
 file "#{node['openresty']['dir']}/conf.d/garage.conf" do
   content <<-EOF
 upstream garage_web {
@@ -40,8 +42,12 @@ end
 #
 
 node['garage']['s3_web_domains'].each do |domain_name|
+  second_level_domain = domain_name.match(/(?:.*\.)?([^.]+\.[^.]+)$/) { $1 }
+  proxy_validation = !gandi_api_credentials["domains"].include?(second_level_domain)
+
   tls_cert_for domain_name do
     auth "gandi_dns"
+    acme_domain "letsencrypt.kosmos.org" if proxy_validation
     action :create
   end