Use count_records method for counting records instead of AR count method.

Author: lgebhardt

lib/jsonapi/processor.rb

@@ -160,7 +160,7 @@ def show_related_resources
         records = resource_klass.filter_records(filters, {},
                                                 related_resource_records)
 
-        record_count = records.count(:all)
+        record_count = resource_klass.count_records(records)
       end
 
       if (JSONAPI.configuration.top_level_meta_include_page_count && record_count)