Sérgio Rodrigues

The idea of this issue is about creating an Error struct to encapsulate all the errors.

https://github.com/ietf-wg-acme/acme/blob/master/draft-ietf-acme-acme.md#account-deactivation

https://github.com/ietf-wg-acme/acme/blob/master/draft-ietf-acme-acme.md#account-key-rollover-account-key-roll-over

https://github.com/ietf-wg-acme/acme/blob/master/draft-ietf-acme-acme.md#account-update

Use [Phoenix.Presence](https://hexdocs.pm/phoenix/Phoenix.Presence.html) instead of manage the players list in an agent.