Shared transport for the App Store Connect API.
Everything the domain crates need and nothing they disagree about: the ES256 JWT auth, the HTTP client that caches those tokens, the JSON:API envelope generics, and the error type.
The domain crates (smbcloud-ascapi-aso for App Metadata,
smbcloud-ascapi-signing for certificates) add their resources as
extension traits on [Client], since Rust only allows inherent impls
in the crate that defines a type. Import a domain crate's prelude to
call its methods on a client.