Restructure src/ and tests/ from package-by-type to package-by-domain

All classes are now organised by domain (Availability, Booking, Auth).
Each domain package contains its value object, repository, admin controller,
REST endpoint, and any shortcode pages under a matching sub-namespace.
Cross-cutting wiring (Plugin, AdminMenu, RestRegistrar, ShortcodeRegistrar,
Schema) lives at src/ root. Tests mirror the domain structure.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

tests/Unit/Auth/RoleManagerTest.php

@@ -0,0 +1,70 @@
+<?php
+declare(strict_types=1);
+
+namespace Unsupervised\Schedular\Tests\Unit\Auth;
+
+use Brain\Monkey\Functions;
+use Unsupervised\Schedular\Auth\RoleManager;
+use Unsupervised\Schedular\Tests\Unit\TestCase;
+
+class RoleManagerTest extends TestCase
+{
+    public function testRegisterAddsInitHook(): void
+    {
+        Functions\expect('add_action')
+            ->once()
+            ->with('init', \Mockery::any());
+
+        (new RoleManager())->register();
+    }
+
+    public function testCreateRolesSkipsExistingRoles(): void
+    {
+        Functions\when('get_role')->alias(static fn() => new \stdClass());
+        Functions\expect('add_role')->never();
+
+        (new RoleManager())->createRoles();
+    }
+
+    public function testCreateRolesAddsInstructorRoleWithCorrectCaps(): void
+    {
+        Functions\when('get_role')->alias(static function (string $role): ?object {
+            return $role === RoleManager::INSTRUCTOR ? null : new \stdClass();
+        });
+
+        Functions\expect('add_role')
+            ->once()
+            ->with(
+                RoleManager::INSTRUCTOR,
+                \Mockery::any(),
+                \Mockery::on(static function (array $caps): bool {
+                    return ($caps['read'] ?? false) === true
+                        && ($caps[RoleManager::CAP_MANAGE_AVAILABILITY] ?? false) === true
+                        && ($caps[RoleManager::CAP_VIEW_LESSONS] ?? false) === true;
+                })
+            );
+
+        (new RoleManager())->createRoles();
+    }
+
+    public function testCreateRolesAddsStudentRoleWithCorrectCaps(): void
+    {
+        Functions\when('get_role')->alias(static function (string $role): ?object {
+            return $role === RoleManager::STUDENT ? null : new \stdClass();
+        });
+
+        Functions\expect('add_role')
+            ->once()
+            ->with(
+                RoleManager::STUDENT,
+                \Mockery::any(),
+                \Mockery::on(static function (array $caps): bool {
+                    return ($caps['read'] ?? false) === true
+                        && ($caps[RoleManager::CAP_BOOK_LESSON] ?? false) === true
+                        && ($caps[RoleManager::CAP_VIEW_LESSONS] ?? false) === true;
+                })
+            );
+
+        (new RoleManager())->createRoles();
+    }
+}