Add age verification on sign-up (#34150)

config/locales/activerecord.en.yml

@@ -55,6 +55,8 @@ en:
               too_soon: is too soon, must be later than %{date}
         user:
           attributes:
+            date_of_birth:
+              below_limit: is below the age limit
             email:
               blocked: uses a disallowed e-mail provider
               unreachable: does not seem to exist