Macro aws_util::client::gen_client_builder

macro_rules! gen_client_builder {
    ($client : ident, $name : ident) => { ... };
    ($client : ident, $name : ident, $client_name : expr) => { ... };
}

Create a function that calls ::new() with credentials sources

Unfortunately there is no trait that we can rely on in Rusoto to allow us to turn this into a generic function, and also we can’t break most of the internal complexity out into its own function because, despite the fact that all clients in Rusoto box their credential providers to avoid being type-parameterized, they expect a concrete type and so StaticCredentials/RefreshingCredentials can’t be returned from the same function.