[Feature request] Support not equal to filter

It will be good if we provide a filter for not equal conditions.

Example

  product_schema = {
     "name" =>  "products",
     "fields" => [
         { "name" => "name", "type" => "string" },
         { "name" => "available_months",  "type" => "string[]" },
         ........
       ]
    }

In the above schema, there is no way to filter such products that has no available months set
i.e available_months != [](empty array)

The issue names no file or test entry point. Start by locating the filter implementation and existing filter tests, then confirm how an inequality against an empty array should be represented; done means products with non-empty available_months can be returned while empty arrays are excluded.