Function collect_local_keys 

async fn collect_local_keys<F>(
    services: &Services,
    users: &[(&'_ UserId, &'_ Vec<OwnedDeviceId>)],
    sender_user: Option<&UserId>,
    allowed_signatures: &F,
    include_display_names: bool,
) -> Keys
where
    F: Fn(&UserId) -> bool + Send + Sync,