add test for meta

t/registry-schema.t

@@ -37,4 +37,16 @@ sub schema_serialize ( $schema, $data ) {
       ->serialize($data);
 }
 
+like(
+    Dancer2::Plugin::JsonApi::Registry::Schema->new(
+        type => 'thing',
+        top_level_meta => {
+            foo => 1,
+            bar => sub ( $data, $xtra ) {
+                $xtra->{bar};
+            }
+        }
+    )->top_level_serialize( {}, { bar => 'yup' } ),
+    { meta => { foo => 1, bar => 'yup' } } );
+
 done_testing();