DLP: regional identifiers and templates

Phase 2b of the DLP and mail flow rules spec: every identifier in the
§2.3 catalog, each implemented from its issuer's published rules and
tested against published examples.

US (SSN, ITIN, EIN, ABA routing, driver's licenses, MBI, NPI, DEA), UK
(NI number, NHS number, UTR), Canada (SIN), Australia (TFN, Medicare),
the EU (Germany's tax ID and ID card, France's NIR, Spain's DNI/NIE,
Italy's codice fiscale, the Dutch BSN, Belgium's national number,
Poland's PESEL, Sweden's personnummer, Denmark's CPR, Finland's HETU,
Ireland's PPS, Portugal's NIF, Austria's SVNR), Norway, Switzerland,
India (Aadhaar, PAN), China, Japan, Singapore, South Korea, Brazil (CPF,
CNPJ), Mexico (CURP) and South Africa. 49 detectors in all, plus seven
templates named for what they find.

An identifier that is only digits and whose check about one random
number in ten passes counts alone only in its written form
(536-22-1234, 943 476 5919) and as bare digits only beside a word; ABA
routing numbers and NPIs always need one. Spec §2.3 records this.

A test runs every detector over an ordinary business email (order,
invoice and tracking numbers, dates, amounts, an address) and requires
nothing to fire but the contact detectors. 47 unit tests.

crates/features/src/mailflow/detectors/any.rs

@@ -6,7 +6,9 @@
 
 //! Detectors that aren't tied to one country (§2.3, region "Any").
 
-use super::{Detector, Findings, Region, Strength, checks, digits, stands_alone, word_near};
+use super::{
+    Detector, Findings, Region, Strength, checks, digits, stands_alone, valid_date, word_near,
+};
 use regex::Regex;
 use std::sync::LazyLock;
 
@@ -295,19 +297,6 @@ const BIRTH_WORDS: &[&str] = &[
     "nascimento",
 ];
 
-fn valid_date(year: u32, month: u32, day: u32) -> bool {
-    let days = match month {
-        1 | 3 | 5 | 7 | 8 | 10 | 12 => 31,
-        4 | 6 | 9 | 11 => 30,
-        2 if year.is_multiple_of(4) && (!year.is_multiple_of(100) || year.is_multiple_of(400)) => {
-            29
-        }
-        2 => 28,
-        _ => return false,
-    };
-    (1900..=2100).contains(&year) && (1..=days).contains(&day)
-}
-
 fn month_number(name: &str) -> u32 {
     const MONTHS: [&str; 12] = [
         "jan", "feb", "mar", "apr", "may", "jun", "jul", "aug", "sep", "oct", "nov", "dec",