OptionalallowSend parameter names that are not in SEARCH_PARAMS — for a filter the API
offers that this client does not model (its facets show befristung,
arbeitszeit, …). Default false: an unknown name is rejected, because the API
ignores one it doesn't know (a typo such as wos) and returns the unfiltered set.
Such a value must still be a string, a finite number or a boolean.
Options for
search().