~ Invitation mail header can now be changed

app/views/mailer_modules/_header.html.erb

@@ -1,7 +1,15 @@
 <table border="0" cellpadding="0" cellspacing="0" width="100%">
   <tr>
     <td bgcolor="#ffffff">
-      <div align="center" style="padding: 0px 15px 0px 15px; <%= invitation.present? ? "background-image: url('http://carto-email-assets.s3.amazonaws.com/confetti.png'); background-position: center top; background-repeat: no-repeat;" : "" %>">
+      <div align="center" style="padding: 0px 15px 0px 15px; <%=
+          invitation.present? \
+            ? (
+              "background-image: url('" +
+                 (Cartodb.get_config(:mailer, 'template', 'header_confetti_url')  || 'http://carto-email-assets.s3.amazonaws.com/confetti.png') +
+              "'); background-position: center top; background-repeat: no-repeat;"
+            ) \
+            : ""
+      %>">
         <table border="0" cellpadding="0" cellspacing="0" width="100%" style="max-width: 620px; width: 100% !important;">
           <tr>
             <td style="padding: 20px 0px 65px 0px;" class="logo">