Added subscribe failure notification

Fixes #738

assets/css/screen.css

@@ -2584,7 +2584,7 @@ Usage (In Ghost editor):
 /* 10. Subscribe Message and Overlay
 /* ---------------------------------------------------------- */
 
-.subscribe-success-message {
+.subscribe-notification {
     position: fixed;
     top: 0;
     right: 0;
@@ -2598,26 +2598,35 @@ Usage (In Ghost editor):
     transform: translateY(-175%);
 }
 
+.subscribe-notification.subscribe-failure-message {
+    background: var(--red);
+}
+
 .subscribe-success .subscribe-success-message {
     visibility: visible;
     transform: translateY(0);
 }
 
-.subscribe-success-message.close {
+.subscribe-failure .subscribe-failure-message {
+    visibility: visible;
+    transform: translateY(0);
+}
+
+.subscribe-notification.close {
     visibility: hidden;
     transition: all 1.35s cubic-bezier(0.19, 1, 0.22, 1);
     transform: translateY(-175%);
 }
 
-.subscribe-success-message .subscribe-close-button {
+.subscribe-notification .subscribe-close-button {
     left: 0;
     top: 0;
     width: 100%;
     height: 100%;
 }
 
-.subscribe-success-message .subscribe-close-button:before,
-.subscribe-success-message .subscribe-close-button:after {
+.subscribe-notification .subscribe-close-button:before,
+.subscribe-notification .subscribe-close-button:after {
     top: 31px;
     right: 20px;
     width: 18px;

default.hbs

@@ -42,10 +42,14 @@
 
     {{!-- The big email subscribe modal content --}}
     {{#if @labs.members}}
-    <div class="subscribe-success-message">
+    <div class="subscribe-notification subscribe-success-message">
         <a class="subscribe-close-button" href="javascript:;"></a>
         You've successfully subscribed to {{@site.title}}!
     </div>
+    <div class="subscribe-notification subscribe-failure-message">
+        <a class="subscribe-close-button" href="javascript:;"></a>
+        Could not sign up! Invalid sign up link.
+    </div>
 
     <div id="subscribe" class="subscribe-overlay">
         <a class="subscribe-close-overlay" href="#"></a>
@@ -102,14 +106,19 @@
 
         // Give the parameter a variable name
         var action = getParameterByName('action');
+        var success = getParameterByName('success');
 
         $(document).ready(function () {
-            if (action == 'subscribe') {
-                $('body').addClass("subscribe-success");
+            if (action == 'subscribe' && (success === null || success === 'true')) {
+                $('body').addClass('subscribe-success');
             }
 
-            $('.subscribe-success-message .subscribe-close-button').click(function () {
-                $('.subscribe-success-message').addClass('close');
+            if (action == 'subscribe' && success === 'false') {
+                $('body').addClass('subscribe-failure');
+            }
+
+            $('.subscribe-notification .subscribe-close-button').click(function () {
+                $('.subscribe-notification').addClass('close');
             });
 
             // Reset form on opening subscrion overlay