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

Beginne damit, den verlinkten Gist zu prüfen und den vorhandenen Einstiegspunkt für die Ressourcenfilterung im Repository zu finden. Vergleiche das aktuelle Verhalten für Ressourcen, die eine Ebene tief verschachtelt sind, mit der angeforderten tieferen Verschachtelung und den has_one-Beziehungen. Erledigt ist die Aufgabe, wenn verschachtelte Filter auf mehreren Einbindungsebenen funktionieren, einschließlich has_one-Ressourcen, und Projekttests dieses Verhalten abdecken.