Set default_url for email notification

Email notifications about task status changes triggered from Gerrit do
not include correct Story URL. Setting the default StoryBoard URL should
fix that issue.

Change-Id: Ic639e344921c4265d3471ac9bd591a4ae489ae52
Story: 2001410
Task: 6106

manifests/application.pp

@@ -58,6 +58,7 @@ class storyboard::application (
 
   $enable_email           = 'True',
   $sender_email_address   = 'no-reply@storyboard.example.org',
+  $default_url            = 'https://storyboard.example.org',
   $smtp_host              = 'localhost',
   $smtp_port              = 25,
 

templates/storyboard.conf.erb

@@ -160,6 +160,9 @@ reply_to = <%= @reply_to_email_address %>
 
 <% end %>
 
+# The default url base to use in emails, if Referer is not set.
+default_url = <%= @default_url %>
+
 # The SMTP server to use.
 smtp_host = <%= @smtp_host %>