Currently only persons in content type "Author" are allowed. This is an unnecessary limitation.
- Each Content Type which has a document type Person (or inherits Person) need to be included in the select2 autosuggest
- integrated_author_widget searches with the contentcontroller index action, now 'contenttypes': 'author' is passed as argument, that should be changed to all contentTypes that are instaceof Person.
- create twig extension that resolves contentTypes (filterInstanceOf method of ContentManager)