Macro provider 

macro_rules! provider {
    (
        name: $name:expr,
        $(version: $version:expr,)?
        $(description: $description:expr,)?
        $(dependencies: [$($dep:expr),* $(,)?],)?
        $(defer_boot: $defer:expr,)?
        $(optional: $optional:expr,)?
        register: |$builder:ident| $register:block
        $(, boot: |$container:ident| $boot:block)?
    ) => { ... };
}

Macro to simplify provider creation