Function paged 

pub fn paged<T>(
    max_pages: usize,
    fetch: impl FnMut(Option<&str>) -> Result<(Vec<T>, Option<String>), String>,
) -> Result<Vec<T>, String>

Every item of a paged API, fetch handed each page’s token. At most max_pages pages: an API that keeps handing back a token would be a loop on a worker nobody is watching.