Add email domain NFC normalization

IDNA, which we use for other minfraud libraries, requires NFC
normalization before punycoding. This adds said NFC normalization
to the email domain.

Author: ugexe

CHANGELOG.md

@@ -27,6 +27,8 @@ CHANGELOG
   become `gmail.com`.
 * Additional `gmail.com` typos are now normalized when `hashAddress` is
   used. For example, `gmali.com` will become `gmail.com`.
+* When `hashAddress` is used, the domain part of an email address is now
+  normalized to NFC.
 
 6.0.0 (2023-12-05)
 ------------------

src/request/email.spec.ts

@@ -216,6 +216,16 @@ describe('Email()', () => {
       md5: md5('[email protected]'),
       domain: 'example.comcom',
     },
+    {
+      email: 'example@bu\u0308cher.com',
+      md5: '2b21bc76dab3c8b1622837c1d698936c',
+      domain: 'bu\u0308cher.com',
+    },
+    {
+      email: 'example@b\u00FCcher.com',
+      md5: '2b21bc76dab3c8b1622837c1d698936c',
+      domain: 'b\u00FCcher.com',
+    },
   ];
 
   test.each(normalizeTests)('%p', (arg) => {

src/request/email.ts

@@ -363,7 +363,7 @@ export default class Email implements EmailProps {
     // We don't need to strip a trailing '.' because validation (isEmail())
     // rejects domains that have it.
 
-    domain = punycode.toASCII(domain);
+    domain = punycode.toASCII(domain.normalize('NFC'));
 
     domain = domain.replace(/(?:\.com){2,}$/, '.com');
     domain = domain.replace(/^\d+(?:gmail?\.com)$/, 'gmail.com');