Name people by their name, not their email address

Anywhere the plugin named a person it could show their email instead —
"Managed by [email protected]" in the students table, the same under
Booked by, instructor names on the class pages.

WordPress defaults a new account's `nickname` to its `user_login`, and
signup uses the email address as the login. So every self-registered
account carried its own address as its nickname, and UserName::format()
fell straight through to it. The name they typed was in `display_name`
all along. Accounts created by a guardian were never affected —
GuardianService::createChild() sets `nickname` outright, which is exactly
why children read correctly and their parents did not.

UserName::format() now walks nickname then display name, skipping either
when it is really the login or the email, so existing accounts read
correctly with nothing to migrate. An identifier still never reaches the
screen: an account with nothing but its address on file falls back to the
id, as before. Signup also sets `nickname` at insert, so new accounts are
right at the source rather than relying on the fallback.

Tests: composer test (866), composer lint, composer cs all pass.

Co-Authored-By: Claude Opus 5 <[email protected]>

tests/Unit/Auth/UserNameTest.php

@@ -9,12 +9,21 @@ use Unsupervised\Schedular\Tests\Unit\TestCase;
 
 class UserNameTest extends TestCase
 {
-    private function user(string $first, string $last, string $nickname): \WP_User
-    {
+    private function user(
+        string $first,
+        string $last,
+        string $nickname,
+        string $displayName = '',
+        string $login = 'ada_login',
+        string $email = '[email protected]',
+    ): \WP_User {
         $user = Mockery::mock(\WP_User::class);
-        $user->first_name = $first;
-        $user->last_name  = $last;
-        $user->nickname   = $nickname;
+        $user->first_name   = $first;
+        $user->last_name    = $last;
+        $user->nickname     = $nickname;
+        $user->display_name = $displayName;
+        $user->user_login   = $login;
+        $user->user_email   = $email;
 
         return $user;
     }
@@ -34,6 +43,60 @@ class UserNameTest extends TestCase
         self::assertSame('Countess', UserName::format($this->user('', '', 'Countess')));
     }
 
+    /**
+     * WordPress defaults a new account's nickname to its `user_login`, and signup
+     * uses the email address as the login — so a self-registered account carried
+     * its own address as its nickname and every screen naming that person showed
+     * the address. The name they typed was in `display_name` all along.
+     */
+    public function testSkipsANicknameThatIsReallyTheLoginAndUsesTheDisplayName(): void
+    {
+        $user = $this->user(
+            '',
+            '',
+            '[email protected]',
+            'Grace Hopper',
+            login: '[email protected]',
+            email: '[email protected]',
+        );
+
+        self::assertSame('Grace Hopper', UserName::format($user, 42));
+    }
+
+    public function testSkipsANicknameThatIsReallyTheEmailAddress(): void
+    {
+        $user = $this->user(
+            '',
+            '',
+            '[email protected]',
+            'Grace Hopper',
+            login: 'gracehopper',
+            email: '[email protected]',
+        );
+
+        // Case-insensitively: the address is the address however it was typed.
+        self::assertSame('Grace Hopper', UserName::format($user, 42));
+    }
+
+    /**
+     * The whole point of the class: an identifier never reaches the screen, even
+     * when it is the only thing on file. Someone who registered without giving a
+     * name is shown as their id rather than as their email address.
+     */
+    public function testNeverFallsThroughToAnIdentifier(): void
+    {
+        $user = $this->user(
+            '',
+            '',
+            '[email protected]',
+            '[email protected]',
+            login: '[email protected]',
+            email: '[email protected]',
+        );
+
+        self::assertSame('42', UserName::format($user, 42));
+    }
+
     public function testFallsBackToIdWhenNothingSet(): void
     {
         self::assertSame('42', UserName::format($this->user('', '', ''), 42));