Show instructor real name or nickname in group-class views, not the login

Add Auth\UserName::format(), which prefers a user's first + last name, then
their nickname, avoiding display_name (which can be the login/username).
Route the instructor name through it in both the front-end offerings response
(instructor_name) and the back-end group-class summary and details views.

Tests: composer test (513), composer lint, composer cs all pass.

Co-Authored-By: Claude Opus 4.8 <[email protected]>

src/Auth/UserName.php

@@ -0,0 +1,35 @@
+<?php
+declare(strict_types=1);
+
+namespace Unsupervised\Schedular\Auth;
+
+/**
+ * Resolves a person's public-facing name for display. Prefers their real name
+ * (first + last), then their nickname — deliberately avoiding the account's
+ * login/username, which `display_name` can otherwise expose.
+ */
+class UserName {
+
+	/**
+	 * The display name for a user: "First Last" when a real name is set,
+	 * otherwise the WordPress nickname. Falls back to the numeric id (or an empty
+	 * string when none is given) when the user cannot be loaded or has no name.
+	 */
+	public static function format( ?\WP_User $user, int $fallbackId = 0 ): string {
+		if ( ! $user instanceof \WP_User ) {
+			return $fallbackId > 0 ? (string) $fallbackId : '';
+		}
+
+		$full = trim( $user->first_name . ' ' . $user->last_name );
+		if ( '' !== $full ) {
+			return $full;
+		}
+
+		$nickname = trim( $user->nickname );
+		if ( '' !== $nickname ) {
+			return $nickname;
+		}
+
+		return $fallbackId > 0 ? (string) $fallbackId : '';
+	}
+}

src/GroupClass/GroupClassController.php

@@ -8,6 +8,7 @@ use Unsupervised\Schedular\Auth\InviteRepository;
 use Unsupervised\Schedular\Auth\RegistrationController;
 use Unsupervised\Schedular\Auth\RegistrationMailer;
 use Unsupervised\Schedular\Auth\RoleManager;
+use Unsupervised\Schedular\Auth\UserName;
 use Unsupervised\Schedular\Offering\Offering;
 use Unsupervised\Schedular\Offering\OfferingRepository;
 use Unsupervised\Schedular\Payment\Payment;
@@ -73,12 +74,10 @@ class GroupClassController {
 
 		$rows = array_map(
 			function ( Offering $offering ): array {
-				$instructor = get_userdata( $offering->instructorId );
-
 				return [
 					'id'          => $offering->id,
 					'title'       => $offering->title,
-					'instructor'  => $instructor ? $instructor->display_name : (string) $offering->instructorId,
+					'instructor'  => $this->instructorName( $offering ),
 					'when'        => $this->whenLabel( $offering ),
 					'capacity'    => $offering->capacity,
 					'enrolled'    => $this->enrollments->countActiveForOffering( (int) $offering->id ),
@@ -196,10 +195,8 @@ class GroupClassController {
 			];
 		}
 
-		$instructor = get_userdata( $offering->instructorId );
-
 		return $this->classSummary( $offering, $enrollments ) + [
-			'instructor'    => $instructor ? $instructor->display_name : (string) $offering->instructorId,
+			'instructor'    => $this->instructorName( $offering ),
 			'price'         => $offering->price,
 			'currency'      => $offering->currency,
 			'duration'      => $offering->durationMinutes,
@@ -211,6 +208,17 @@ class GroupClassController {
 		];
 	}
 
+	/**
+	 * The teaching instructor's display name — their real name or nickname, never
+	 * the login. Falls back to the numeric id when the account is gone. See
+	 * {@see UserName::format()}.
+	 */
+	private function instructorName( Offering $offering ): string {
+		$user = get_userdata( $offering->instructorId );
+
+		return UserName::format( $user instanceof \WP_User ? $user : null, $offering->instructorId );
+	}
+
 	/**
 	 * Human-readable "when" label for a class: the class date (or weekly date
 	 * range) and, when set, the start time. Empty when the class has no date.

src/Offering/OfferingEndpoint.php

@@ -4,6 +4,7 @@ declare(strict_types=1);
 namespace Unsupervised\Schedular\Offering;
 
 use Unsupervised\Schedular\Auth\RoleManager;
+use Unsupervised\Schedular\Auth\UserName;
 use Unsupervised\Schedular\GroupClass\GroupAccessRepository;
 use Unsupervised\Schedular\Val;
 
@@ -84,8 +85,9 @@ class OfferingEndpoint {
 	}
 
 	/**
-	 * A public-facing offering array with the assigned instructor's display name
-	 * added (empty when the instructor account no longer exists).
+	 * A public-facing offering array with the assigned instructor's name added —
+	 * their real name or nickname, never the login (empty when the instructor
+	 * account no longer exists). See {@see UserName::format()}.
 	 *
 	 * @return array<string, mixed>
 	 */
@@ -93,7 +95,7 @@ class OfferingEndpoint {
 		$out  = $offering->toArray( includeEtransferEmail: false );
 		$user = get_userdata( $offering->instructorId );
 
-		$out['instructor_name'] = $user instanceof \WP_User ? $user->display_name : '';
+		$out['instructor_name'] = UserName::format( $user instanceof \WP_User ? $user : null );
 
 		return $out;
 	}