Add error flash messages

app/views/main.scala.html

@@ -89,6 +89,9 @@
 
 <div class="container" id="main">
     <h1>@title</h1>
+    @for(error <- header.flash.get("error")){
+        <div class="alert alert-danger alert-dismissible">@error</div>
+    }
     @content
 
     <hr>