[15.x] Indicate if invoice is paid (#1686)

* Indicate if invoice is paid

* No amount due when paid

* wip

* wip

Author: driesvints

resources/views/invoice.blade.php

@@ -49,9 +49,13 @@
 <div class="container">
     <table style="margin-left: auto; margin-right: auto;" width="100%">
         <tr valign="top">
-            <td width="160">
+            <td width="180">
                 <span style="font-size: 28px;">
                     Invoice
+
+                    @if ($invoice->paid)
+                        <span style="color: #0c0; font-size: 20px;">(Paid)</span>
+                    @endif
                 </span>
 
                 <!-- Invoice Info -->