These filter API v2 features were cut late in development because the form encoding version is hard to implement correctly and because I thought no clients actually used `keywords_attributes`. Unfortunately, Phanpy does use `keywords_attributes`.
* Use correct entity name
* We support server-side filters now
* Document filter v1 methods that can throw a 409
* Validate v1 filter phrase as filter title
* Always check v1 filter API status codes in tests
* Document keyword minimum requirement on filter API v1
* Make it possible to specify filter keyword update columns per filter keyword
* Implement v2 filter API
* Fix lint and tests
* Update Swagger spec
* Fix filter update test
* Update Swagger spec *correctly*
* Update actual files Swagger spec was generated from
* Remove keywords_attributes and statuses_attributes
* Add test for serialization of empty filter
* More helpful messages when object is owned by wrong account
