username: now optional, if defined 2..64 chars
password: now optional (no mode __NO_PASSWORD...__)
oidc: now optional
important: if need Nextcloud, username must be defined
- SMTP has a mock to enable end to end test and validate the whole path
(via OXICLOUD_SMTP_MOCK)
- add email normalisation ( including punicode)
- api to share to external user