Default to string in api doc for search params where type cannot be deduced
Api doc generation is not able to determine search parameter types when generated without a migrated database (e.g. with nulldb). These types aren't enforced and are always sent to the api as a string (as part of url parameters).
We can default to string value in this case as a safe fallback, and allow users to regenerate the apidoc manually if they require a more specific information (e.g. integer fields).