Let the studio register the students who cannot register themselves

The Book a lesson for a student panel built its picker from the us_student
role but vetted the submission with the book_lesson capability. ChildLoginGate
and RegistrationLoginGate withhold that capability from accounts that keep the
role, so the panel offered every guardian-managed child and every unapproved
signup and then refused them — with a message claiming no student had been
chosen, and a form cleared of all five fields.

Withholding book_lesson stops those accounts registering in their own name. It
was never meant to stop the studio acting for them, which is what the panel is
for, and for a child is the only route to a lesson besides their guardian.

Guard the student role instead, via a new RoleManager::isStudent() shared with
every picker and guard on the staff side so the two cannot drift apart again.
Group enrolment gets the same predicate: addDirect() and grantAccess() vetted
their posted ids not at all, and would enrol an instructor, an administrator,
or an account deleted since the page was drawn — raising a real payment against
them for a priced class.

Keep a refused booking's fields as submitted, reading the form through one
LessonController::submittedBooking() so what gets booked and what is shown
again cannot disagree about a field name. A booking that succeeds still leaves
an empty form, so the next one does not inherit it.

Closes #185

Co-Authored-By: Claude Opus 5 <[email protected]>
Claude-Session: https://claude.ai/code/session_01XunBYk2sFEc1oL14sUiuBU

tests/Unit/Booking/AdminBookingTest.php

@@ -5,6 +5,7 @@ namespace Unsupervised\Schedular\Tests\Unit\Booking;
 
 use Brain\Monkey\Functions;
 use Mockery;
+use Unsupervised\Schedular\Auth\RoleManager;
 use Unsupervised\Schedular\Availability\AvailabilityRepository;
 use Unsupervised\Schedular\Availability\AvailabilitySlot;
 use Unsupervised\Schedular\Booking\AdminBooking;
@@ -36,10 +37,10 @@ class AdminBookingTest extends TestCase
         Functions\when('mysql2date')->alias(
             static fn (string $format, string $date): string => date($format, (int) strtotime($date))
         );
-        Functions\when('get_userdata')->justReturn(false);
+        // The picker offers holders of the student role, and that is what the guard
+        // accepts; it is exercised on its own below.
+        Functions\when('get_userdata')->alias(fn (int $id): \WP_User => $this->user($id, 'Jane Doe'));
         Functions\when('get_users')->justReturn([]);
-        // Everyone offered in the picker can book; the guard is exercised on its own.
-        Functions\when('user_can')->justReturn(true);
         // The staff member doing the booking; stamped on the lesson as booked_by.
         Functions\when('get_current_user_id')->justReturn(3);
 
@@ -175,9 +176,9 @@ class AdminBookingTest extends TestCase
         self::assertSame('slot_taken', $result->get_error_code());
     }
 
-    public function testSomeoneWhoCannotBookLessonsIsRefused(): void
+    public function testSomeoneWhoIsNotAStudentIsRefused(): void
     {
-        Functions\when('user_can')->justReturn(false);
+        Functions\when('get_userdata')->alias(fn (int $id): \WP_User => $this->user($id, 'Jane Doe', [RoleManager::INSTRUCTOR]));
         $this->availability->shouldReceive('findById')->never();
 
         $result = $this->admin->book(42, 7, 3, Lesson::RECURRENCE_SINGLE, false, '');
@@ -186,6 +187,69 @@ class AdminBookingTest extends TestCase
         self::assertSame('invalid_student', $result->get_error_code());
     }
 
+    public function testAnAccountThatNoLongerExistsIsRefused(): void
+    {
+        Functions\when('get_userdata')->justReturn(false);
+        $this->availability->shouldReceive('findById')->never();
+
+        $result = $this->admin->book(42, 7, 3, Lesson::RECURRENCE_SINGLE, false, '');
+
+        self::assertInstanceOf(\WP_Error::class, $result);
+        self::assertSame('invalid_student', $result->get_error_code());
+    }
+
+    public function testNoStudentChosenIsRefusedWithoutLookingAnyoneUp(): void
+    {
+        Functions\expect('get_userdata')->never();
+        $this->availability->shouldReceive('findById')->never();
+
+        $result = $this->admin->book(0, 7, 3, Lesson::RECURRENCE_SINGLE, false, '');
+
+        self::assertInstanceOf(\WP_Error::class, $result);
+        self::assertSame('invalid_student', $result->get_error_code());
+    }
+
+    /**
+     * A child holds the student role but never `book_lesson` — withheld so the
+     * account cannot book in its own name. The studio booking for them is the only
+     * route a child has to a lesson, so it must not be blocked by that.
+     */
+    public function testBooksForAGuardiansChildWhoCannotBookThemselves(): void
+    {
+        Functions\when('user_can')->justReturn(false);
+        $this->availability->shouldReceive('findById')->with(7)->andReturn($this->slot());
+        $this->offerings->shouldReceive('findById')->with(3)->andReturn($this->offering());
+        $this->availability->shouldReceive('claim')->once()->with(7)->andReturn(true);
+        $this->bookings->shouldReceive('insert')->once()->andReturn(100);
+        $this->payments->shouldReceive('createForRegistration')->once()->andReturn($this->pendingPayment());
+
+        $notice = $this->admin->book(42, 7, 3, Lesson::RECURRENCE_SINGLE, false, '');
+
+        self::assertIsString($notice);
+        self::assertStringContainsString('30 min piano', $notice);
+    }
+
+    /**
+     * Same for a self-signup the studio has not approved yet: the front desk can
+     * still get them onto the calendar while the paperwork catches up.
+     */
+    public function testBooksForAStudentStillAwaitingApproval(): void
+    {
+        Functions\when('user_can')->justReturn(false);
+        $this->availability->shouldReceive('findById')->with(7)->andReturn($this->slot());
+        $this->offerings->shouldReceive('findById')->with(3)->andReturn($this->offering());
+        $this->availability->shouldReceive('claim')->once()->with(7)->andReturn(true);
+        $this->bookings->shouldReceive('insert')->once()->with(Mockery::on(
+            static fn (Lesson $l): bool => 42 === $l->studentId
+        ))->andReturn(100);
+        $this->payments->shouldReceive('createForRegistration')->once()->andReturn($this->pendingPayment());
+
+        $notice = $this->admin->book(42, 7, 3, Lesson::RECURRENCE_SINGLE, false, '');
+
+        self::assertIsString($notice);
+        self::assertStringContainsString('pending payment', $notice);
+    }
+
     public function testATiedTimeCannotBeBookedAsADifferentLessonType(): void
     {
         $this->availability->shouldReceive('findById')->with(7)->andReturn($this->slot(offeringId: 3));
@@ -299,10 +363,12 @@ class AdminBookingTest extends TestCase
         );
     }
 
-    private function user(int $id, string $name): \WP_User
+    /** @param list<string> $roles */
+    private function user(int $id, string $name, array $roles = [RoleManager::STUDENT]): \WP_User
     {
         $user               = Mockery::mock(\WP_User::class);
         $user->ID           = $id;
+        $user->roles        = $roles;
         $user->first_name   = '';
         $user->last_name    = '';
         $user->nickname     = $name;