Macro provider 

macro_rules! provider {
    ($(#[$meta:meta])* $vis:vis static $name:ident : Provider = $init:expr ;) => { ... };
}

Declare a provider static and register it (docs/settings.md):

day_piece_settings::provider! {
    static UPDATES: Provider = Provider { id: "updates", order: 900, available: || true,
        group: updates_group, startup: Some(schedule) };
}