A new filter has been added to the delivery api that lets you search for a specific value with a "like" query.

As example you could search for the author with the name "john" in a field that has the full name "John Mustermann" with like:

/v1/cdn/stories/?filter_query[name][like]=*john*&version=draft&token=6HMYdAjBoONyuS6GIf5PdAtt&starts_with=authors/

Or you can also search for the authors that don't have "john" in their names with not_like:

/v1/cdn/stories/?filter_query[name][not_like]=*john*&version=draft&token=6HMYdAjBoONyuS6GIf5PdAtt&starts_with=authors/

More infos at the delivery api documentation.