[Bug] HttpxRequestAdapter: The silent deprecation of base_url is actually a breaking change

[RadoslavGatev]

#481 actually introduced a breaking change.

The parameter base_url is still there but no matter what value you provide, it's ignored. We did not pass a value for http_client, and only specified the base_url like this:

request_adapter = HttpxRequestAdapter(
    authentication_provider, base_url="https:/example.com"
)

We run this in a Fabric notebook where the version of the package was not pinned. So the moment it downloaded the new version, it failed with a misleading error.

To fix it, we had to do the following work around:

request_adapter = HttpxRequestAdapter(authentication_provider)
request_adapter.base_url = "https:/example.com"

I think it's best to deprecate this base_url parameter in the constructor if it's not supposed to be used.