SMTP credentials

Logins for applications that relay over SMTP rather than HTTP.

• GETList smtp credentials/api/v1/smtp-credentials
• POSTCreate an SMTP credential/api/v1/smtp-credentials
• PATCHUpdate a smtp credential/api/v1/smtp-credentials/{credential}
• DELETEDelete a smtp credential/api/v1/smtp-credentials/{credential}
• GETUsage a smtp credential/api/v1/smtp-credentials/{credential}/usage
• POSTEnable a smtp credential/api/v1/smtp-credentials/{credential}/enable
• POSTRevoke a smtp credential/api/v1/smtp-credentials/{credential}/revoke
• POSTRotate a smtp credential/api/v1/smtp-credentials/{credential}/rotate
• PUTIp Allowlist a smtp credential/api/v1/smtp-credentials/{credential}/ip-allowlist