To make debugging easier, this switches to env_logger and the log crate.
This helps with getting to the output of the underlying crates this
builds on.
BREAKING CHANGE: this changes the output, so if you parse the output in
your scripts, then this might break it.
previously, when the API call would fail (for whatever reason),
the cached IP had already been written, so following executions
wouldn't attempt to update the IP, even though the previous
attempt had failed.
Cloudflare's v4 API provides three ways of authenticating,
with the API tokens being the new, standard conform, recommended
way. This patch removes the use of the old auth_key + email combo
and replaces it with API tokens.
BREAKING CHANGE: auth keys can't be used anymore, switch to api tokens