It is valid for a user to have an apostrophe in their email address. Email address seems to be the defacto value used as an for the system-managed blueprint.

Example:

Port does not appear to support such an email address.

If we attempt to create such a user via the web app:

> j.o'bloggs@ourdomain.com is not a valid email

If we attempt to upsert the entity via the Port APIs, the audit log shows an error:

> "identifier" must match pattern "^[A-Za-z0-9@_.+:\\/=-]+$"