ExtractAuthorization shouldn't be public, but it temporarily is to keep things working.

HTTPMiddleware injects the authorization header into the context.

StreamClientInterceptor does the same for streaming requests.

StreamInterceptor will process the authorization header, convert it to a prefix, and then inject it into the context, but for streams.

UnaryClientInterceptor extracts the auth header value from the context and appends it to the outgoing metadata.

AuthRoundTripper is a http client "middleware" that extracts the auth middleware out of the context and injects it into the request.