feat: resource attribute options

[chesedo]

This makes it possible for resource attributes to take in options like the following:

#[shuttle_service::main]
async fn poem(#[shared::Postgres(size = "10Gb", public = false)] pool: PgPool) -> ShuttlePoem {
    //                           ----------------------------- Options that will be passed to builder
}

This will bring us one step closer to string interpolation from env variables for resource configuration