Make trial banner dismissiable using BS alert

app/assets/stylesheets/framework/header.scss

@@ -318,25 +318,17 @@ header {
   }
 }
 
-.gitlab-ee-trial-banner {
-  padding: $gl-padding;
+.gitlab-ee-trial-banner.alert {
   text-align: center;
 
-  p {
-    margin: 0;
-    display: inline-block;
-
-    a {
+  p a {
+    color: $gl-link-color;
+    text-decoration: none;
     font-weight: bold;
-    }
-  }
-
-  .close-trial-banner {
-    float: right;
-    margin-top: 2px;
 
     &:hover {
-      cursor: pointer;
+      color: $gl-link-hover-color;
+      text-decoration: underline;
     }
   }
 }

app/views/layouts/header/_default.html.haml

 - if license_message.present?
-  .gitlab-ee-trial-banner
-    %p= license_message
-    %button.btn.btn-default.close.close-trial-banner.js-close-trial-banner{ type: 'button', 'aria-label' => 'Dismiss banner' }
+  .alert.alert-dismissible.gitlab-ee-trial-banner.js-gitlab-ee-trial-banner{ role: 'alert' }
+    %button.close{ type: 'button', 'data-dismiss' => 'alert', 'aria-label' => 'Dismiss banner' }
       = icon('times', 'aria-hidden' => 'true')
-%header.navbar.navbar-gitlab{ class: "#{nav_header_class} #{ 'has-trial-banner' if trial_license_message.present?}" }
+    %p
+      = license_message
+  :javascript
+    $('.js-gitlab-ee-trial-banner').on('close.bs.alert', function() { $('.js-navbar-gitlab').removeClass('has-trial-banner'); });
+%header.navbar.navbar-gitlab.js-navbar-gitlab{ class: "#{nav_header_class} #{ 'has-trial-banner' if trial_license_message.present?}" }
   .navbar-border
   %a.sr-only.gl-accessibility{ href: "#content-body", tabindex: "1" } Skip to content
   .container-fluid