primitive BearerAuth
"""
Construct an HTTP Bearer token authentication header value.
Returns a `(name, value)` tuple suitable for passing directly to
`Headers.set()` or the request builder's `header()` method:
`("authorization", "Bearer <token>")`.
"""
fun apply(token: String): (String, String) =>
"""
Build the Bearer auth header from `token`.
"""
("authorization", "Bearer " + token)