Block a user
Email() uses an unauditable mega-regexp; prefer net/mail
email: validate with net/mail.ParseAddress
add Required, Prefix, Suffix, Contains, Match validators
All() is fail-fast; no all-errors-at-once aggregation
add Collect: run every validator and join all errors
Add robots.txt control (allow/disallow search indexing)
serve /robots.txt with opt-in search indexing
cli: read the bind address from the right flag