This is a partial revert of 288d9c999e. For some reason it didn't occur to me
that we could do it this way earlier. Whoops.
This also contains a middleware update: mutation funcs can return an error now
and short-circuit the rest of the request/response flow. The idea here is that
if someone is configuring their kubeclient to use middleware, they are agreeing
to a narrow-er client contract by doing so (e.g., their TokenCredentialRequest's
must have an Spec.Authenticator.APIGroup set).
I also updated some internal/groupsuffix tests to be more realistic.
Signed-off-by: Andrew Keesler <akeesler@vmware.com>
0fc1f17866