Default TreasuryPrime.HTTPClient adapter, built entirely on Erlang's
built-in :httpc (part of the :inets application) and :ssl. This means
treasury_prime has no required HTTP dependency at all — no Req, no
Finch, no Hackney.
TLS certificates are sourced from :public_key.cacerts_get/0 (available
since OTP 25), which uses the OS's trusted CA store. Hostname verification
is enforced via :public_key.pkix_verify_hostname_match_fun/1.
This adapter starts a dedicated, isolated :httpc profile
(:treasury_prime) the first time it's used, so it does not interfere
with :httpc's default profile or any other library/application that
happens to also use :httpc.