[FIXED] Stopped disabling the IAM auth plugin after failed IAM
authentications. Subsequent requests will re-request authorization,
potentially failing again if the original authentication failure was not
temporary.
[FIXED] Ensure IAM API key can be correctly changed.
[FIXED] Callback with an error when a user cannot be authenticated using IAM.
[FIXED] Ensure authorization tokens are not unnecessarily requested.
[IMPROVED] Do not apply cookie authentication by default in the case that no
credentials are provided.
[IMPROVED] Preemptively renew authorization tokens that are due to expire.
4.2.2 (2019-10-23)