pub fn canonicalize_email(address: &str) -> Result<String>Expand description
Canonicalize an email address for storage and matching: case-fold the
whole address and lower-case the domain. This is stronger than
str::to_lowercase, which leaves ß intact; case-folding maps it to ss
so Strauß@Example.com and strauss@example.com collide on one key.
Errors when the address exceeds MAX_EMAIL_LEN or has no @ separating
a non-empty local part from a non-empty domain.