add key as URL parameter to startpage

pass/views/key.ejs

@@ -28,7 +28,7 @@
   <h2><%= req.t("key.tokens", {ns: "key"}) _%></h2>
   <div class="amount"><%= key.key.get_charge() %></div>
   <div><%= req.t("key.valid_until", {ns: "key"}) %> <span><%= key.key.get_expiration_date().format("DD.MM.YYYY") %></span></div>
-  <a href="<%= baseDir.replace("/keys", "") _%>" class="button startpagelink">
+  <a href="<%= baseDir.replace("/keys", "") + `?key=${key.key.get_key()}` _%>" class="button startpagelink">
     <%_ if(key.key.get_charge() > 0) { _%>
     <%= req.t("key.startpagelinks.adfree", {ns: "key"}) _%>
     <%_ } else { _%>