Nested included resources filters

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Description

Hi guys, I'm sorry about how this issue is looking, don't have time to make it better.
Currently, (checked on 0.9.5, and it's probably the same on 0.9.7) filtering on nested resources works only for 1 level deep inclusion, i.e. included_resource.filter_key. I made some monkey-patches in my app, to make it work with nested resources inclusion, i.e. included_resource.another_included_resource.filter_key.
Also, I did some changes to make filters work with has_one relationships.

The code can be a little bit messy, but it's working, at least for my project. No blame, please :)

The code is here: https://gist.github.com/RoM4iK/1ce4eab45ed0ceafa8728ed487ccddbb

まず、リンクされた Gist を確認し、リポジトリ内で既存のリソースフィルタリングのエントリーポイントを見つけます。現在の 1 レベルのネストされたリソースの動作を、要求されているより深いネストおよび has_one リレーションシップと比較します。ネストされたフィルターが複数の包含レベルで機能し、has_one リソースも含まれ、プロジェクトのテストでその動作がカバーされれば完了です。