fn extract_domain_from_user_id(userid: &str) -> Option<&str>Expand description
Returns the domain name in an OpenPGP User ID string, if one is found.
For a userid of the form “Foo bar@baz.org Bleep”, we consider
bar@baz.org the email part, and baz.org the domainname.
If there are additional < or > characters, this returns None.
If there is more than one @ character in the email part, this returns None.
§Note
This is a very naive implementation and will be replaced by a proper type in the future.