I'm currently working on cleaning up the providers mechanism throughout the project which is used in several areas of the client library and POSH module to support extensibility.
One such area is the Vault concept, which is the repository that is used to store client-side state of the ACME protocol including any generated artifacts issued by the ACME CA server (e.g. certificates).
For anyone interested, please review and provide feedback.
Thanks,
-Eugene.