Spec: https://doc.ez.no/display/PR/%28n01%29+Basic+Edit+via+tree+navigation+-+explanations+-+fields+editing#id-%28n01%29BasicEditviatreenavigation-explanations-fieldsediting-Keywords
EZP-23916 As a UI developer, I want to have an API to search in the available keywords
EZP-23501 As an editor, I want to be able to fill keyword fields while editing a content