normalize localparts with unicode nfc when parsing

both when parsing our configs, and for incoming on smtp or in messages.
so we properly compare things like é and e+accent as equal, and accept the
different encodings of that same address.

webadmin/api.ts

@@ -43,7 +43,7 @@ export interface IPRevCheckResult {
 // trailing dot. When using with StrictResolver, add the trailing dot.
 export interface Domain {
 	ASCII: string  // A non-unicode domain, e.g. with A-labels (xn--...) or NR-LDH (non-reserved letters/digits/hyphens) labels. Always in lower case. No trailing dot.
-	Unicode: string  // Name as U-labels. Empty if this is an ASCII-only domain. No trailing dot.
+	Unicode: string  // Name as U-labels, in Unicode NFC. Empty if this is an ASCII-only domain. No trailing dot.
 }
 
 export interface MXCheckResult {
@@ -765,6 +765,7 @@ export enum SPFResult {
 // Localpart is a decoded local part of an email address, before the "@".
 // For quoted strings, values do not hold the double quote or escaping backslashes.
 // An empty string can be a valid localpart.
+// Localparts are in Unicode NFC.
 export type Localpart = string
 
 // An IP is a single IP address, a slice of bytes.