Feature Request

Currently, all policies have to be configured on the client at creation time.
A few selected options can be passed per request, via the context.

This makes a client relatively rigid. If we need to make calls to different endpoints (hosts) but with the same client, it's impossible (without non-trivial middlewares).

Allowing to modify the policy stack, or simply append a policy for a single call on an existing client would enable greater flexibility, without adding complexity for the simple use cases.

This could be done either via the options passed to every operations, which currently is often empty

or via the same context extensions as for retry, capture, or HTTPHeaders