fix filtering by included resource

when using of custom filter verifier - context is missing

Author: gigorok

lib/jsonapi/request_parser.rb

@@ -291,7 +291,7 @@ def parse_relationship_filter(key, value)
           return @errors.concat(Exceptions::FilterNotAllowed.new(filter_method).errors)
         end
 
-        verified_filter = relationship.resource_klass.verify_filters(filter_method => value)
+        verified_filter = relationship.resource_klass.verify_filters({ filter_method => value }, @context)
         @include_directives.merge_filter(relationship.name, verified_filter)
       else
         return @errors.concat(Exceptions::FilterNotAllowed.new(filter_method).errors)