feature #58361 [Mailer][Mime] Support unicode email addresses (arnt, OskarStark)

This PR was merged into the 7.2 branch.

Discussion
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[Mailer][Mime] Support unicode email addresses

| Q             | A
| ------------- | ---
| Branch?       | 7.2
| Bug fix?      | no
| New feature?  | yes
| Deprecations? | no
| License       | MIT

This allows applications to send mail to all-Chinese email addresses, or like my test address grå`@gr`å.org. Code that uses Symfony needs no change and should experience no difference, although if the upstream MTA doesn't support it (most do by now) then an exception is thrown slightly later than before this change.

Commits
-------

b1deef8ff3 Reinstate the restriction that the sender's localpart must be all-ASCII.
c11d6e068d Code style conformance and dependency updates.
3fbbb235d6 Resolve code review comments from stof and oska
8597c1ee8d Update src/Symfony/Component/Mime/Address.php
2d74b98061 Fix minor spelling error.
6f07a17bbf Send SMTPUTF8 if the message needs it and the server supports it.
d43b8329f2 Add new accessors to help determine whether to use the SMTPUTF8 extension

Author: fabpot

Address.php

@@ -117,4 +117,24 @@ public static function createArray(array $addresses): array
 
         return $addrs;
     }
+
+    /**
+     * Returns true if this address' localpart contains at least one
+     * non-ASCII character, and false if it is only ASCII (or empty).
+     *
+     * This is a helper for Envelope, which has to decide whether to
+     * the SMTPUTF8 extensions (RFC 6530 and following) for any given
+     * message.
+     *
+     * The SMTPUTF8 extension is strictly required if any address
+     * contains a non-ASCII character in its localpart. If non-ASCII
+     * is only used in domains (e.g. horst@freiherr-von-mühlhausen.de)
+     * then it is possible to to send the message using IDN encoding
+     * instead of SMTPUTF8. The most common software will display the
+     * message as intended.
+     */
+    public function hasUnicodeLocalpart(): bool
+    {
+        return (bool) preg_match('/[\x80-\xFF].*@/', $this->address);
+    }
 }

Tests/AddressTest.php

@@ -81,6 +81,13 @@ public function testCreateArray()
         $this->assertEquals([$fabien], Address::createArray(['[email protected]']));
     }
 
+    public function testUnicodeLocalpart()
+    {
+        /* dømi means example and is reserved by the .fo registry */
+        $this->assertFalse((new Address('info@dømi.fo'))->hasUnicodeLocalpart());
+        $this->assertTrue((new Address('dømi@dømi.fo'))->hasUnicodeLocalpart());
+    }
+
     public function testCreateArrayWrongArg()
     {
         $this->expectException(\TypeError::class);