This allows the token exchange request to be performed with the correct TLS configuration.
We go to a bit of extra work to make sure the `http.Client` object is cached between reconcile operations so that connection pooling works as expected.
Signed-off-by: Matt Moyer <moyerm@vmware.com>
Because we want it to implement an AuthcodeExchanger interface and
do it in a way that will be more unit test-friendly than the underlying
library that we intend to use inside its implementation.
