Fix invite sign-in persistence, add invite-only text option, repair account questions

Three registration fixes reported from live use:

- Accepting an invite now keeps the student signed in. The form was
  processed inside render() during the_content, so wp_set_auth_cookie()
  ran after headers were sent and the cookie never persisted — the new
  student was bounced back to the logged-out registration page. The
  submission is now handled on template_redirect (before output) with a
  post/redirect/get, so the cookie sticks and the student lands logged in.

- The "registration is by invitation only" message is now customisable via
  a new block attribute (inviteOnlyMessage / shortcode invite_only_message),
  falling back to the default wording when blank.

- Account-registration questions save again. dbDelta does not reliably
  relax a column from NOT NULL to NULL, so sites created before account-
  scope questions kept us_questions.offering_id NOT NULL and rejected
  account inserts ("Column 'offering_id' cannot be null"). A one-time,
  self-healing migration (guarded by its own option, not the version gate)
  re-applies the nullable definition on next load.

composer test, composer lint, composer cs all pass.

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

tests/Unit/Auth/RegistrationPageTest.php

@@ -59,11 +59,14 @@ class RegistrationPageTest extends TestCase
             'settings'  => Mockery::mock(StudioSettings::class),
         ];
 
+        $this->ctx['versions']    = Mockery::mock(PolicyVersionRepository::class);
+        $this->ctx['acceptances'] = Mockery::mock(AcceptanceRepository::class);
+
         $this->ctx['page'] = new RegistrationPage(
             $invites,
             $policies,
-            Mockery::mock(PolicyVersionRepository::class),
-            Mockery::mock(AcceptanceRepository::class),
+            $this->ctx['versions'],
+            $this->ctx['acceptances'],
             $this->ctx['settings'],
             $this->ctx['mailer'],
             $questions,
@@ -403,4 +406,98 @@ class RegistrationPageTest extends TestCase
 
         self::assertSame('invite', $this->submit($invite, false));
     }
+
+    public function testMaybeHandleSubmitLogsInInviteAndRedirects(): void
+    {
+        $_POST    = [ 'us_register' => '1', 'password' => 'password123', 'display_name' => 'Ada' ];
+        $_REQUEST = [ 'us_invite' => 'raw-token' ];
+
+        Functions\when('is_user_logged_in')->justReturn(false);
+        Functions\when('check_admin_referer')->justReturn(true);
+        Functions\when('email_exists')->justReturn(false);
+        Functions\when('wp_insert_user')->justReturn(42);
+        Functions\when('is_wp_error')->justReturn(false);
+        Functions\when('get_permalink')->justReturn('http://home.test/register/');
+        Functions\when('add_query_arg')->alias(static fn (string $k, string $v, string $u): string => $u . '?' . $k . '=' . $v);
+
+        // The cookie must be set here — during template_redirect, before output —
+        // which is the whole point of processing the submit outside render().
+        Functions\expect('wp_set_current_user')->once()->with(42);
+        Functions\expect('wp_set_auth_cookie')->once()->with(42);
+
+        $invite = new Invite(email: '[email protected]', token: 'hash', createdAt: '2024-01-01 00:00:00', id: 9);
+        $this->ctx['invites']->shouldReceive('findByToken')->once()->andReturn($invite);
+        $this->ctx['invites']->shouldReceive('markAccepted')->once();
+        $this->ctx['settings']->shouldReceive('openRegistrationEnabled')->andReturn(false);
+
+        $page = Mockery::mock(
+            RegistrationPage::class,
+            [
+                $this->ctx['invites'],
+                $this->ctx['policies'],
+                $this->ctx['versions'],
+                $this->ctx['acceptances'],
+                $this->ctx['settings'],
+                $this->ctx['mailer'],
+                $this->ctx['questions'],
+                $this->ctx['answers'],
+                $this->ctx['access'],
+            ]
+        )->makePartial()->shouldAllowMockingProtectedMethods();
+
+        $captured = '';
+        $page->shouldReceive('redirect')->once()->with(Mockery::on(static function (string $url) use (&$captured): bool {
+            $captured = $url;
+            return true;
+        }));
+
+        $page->maybeHandleSubmit();
+
+        self::assertStringContainsString('us_registered=invite', $captured);
+    }
+
+    public function testMaybeHandleSubmitStoresValidationErrorWithoutRedirecting(): void
+    {
+        // Too-short password: handleSubmit returns an error and no redirect fires.
+        $_POST = [ 'us_register' => '1', 'password' => 'short', 'display_name' => 'Ada' ];
+
+        Functions\when('is_user_logged_in')->justReturn(false);
+        Functions\when('check_admin_referer')->justReturn(true);
+        $this->ctx['settings']->shouldReceive('openRegistrationEnabled')->andReturn(true);
+
+        // A redirect would call exit; reaching the assertion proves none happened.
+        $this->ctx['page']->maybeHandleSubmit();
+
+        $error = (new \ReflectionProperty(RegistrationPage::class, 'submitError'))->getValue($this->ctx['page']);
+        self::assertNotSame('', $error);
+    }
+
+    public function testInviteSuccessRedirectShowsLoggedInWelcome(): void
+    {
+        // After the PRG redirect the student is logged in; the us_registered flag
+        // distinguishes a just-completed signup from an already-logged-in visitor.
+        $_GET = [ 'us_registered' => 'invite' ];
+        Functions\when('is_user_logged_in')->justReturn(true);
+        Functions\when('sanitize_key')->alias(static fn ($v) => strtolower((string) $v));
+
+        $html = $this->ctx['page']->render([]);
+
+        self::assertStringContainsString('us-success', $html);
+        self::assertStringContainsString('now logged in', $html);
+    }
+
+    public function testInviteOnlyMessageCanBeCustomised(): void
+    {
+        // Closed registration and no invite → the invitation-only gate shows.
+        Functions\when('is_user_logged_in')->justReturn(false);
+        Functions\when('sanitize_key')->alias(static fn ($v) => strtolower((string) $v));
+        Functions\when('wp_login_url')->justReturn('http://home.test/wp-login.php');
+        Functions\when('wp_nonce_field')->justReturn('');
+        $this->ctx['settings']->shouldReceive('openRegistrationEnabled')->andReturn(false);
+
+        $html = $this->ctx['page']->render([ 'inviteOnlyMessage' => 'Ask the front desk for a link.' ]);
+
+        self::assertStringContainsString('Ask the front desk for a link.', $html);
+        self::assertStringNotContainsString('by invitation only', $html);
+    }
 }

tests/Unit/BlockRegistrarTest.php

@@ -126,7 +126,7 @@ class BlockRegistrarTest extends TestCase
             array_keys($registered['us-scheduler/student-login']['attributes'])
         );
         self::assertSame(
-            ['loginPageId'],
+            ['loginPageId', 'inviteOnlyMessage'],
             array_keys($registered['us-scheduler/student-register']['attributes'])
         );
         self::assertSame(

tests/Unit/Registration/QuestionRepositoryTest.php

@@ -212,4 +212,28 @@ class QuestionRepositoryTest extends TestCase
 
         self::assertTrue($this->repo->delete(4));
     }
+
+    public function testEnsureOfferingNullableRunsAlterAndReportsSuccess(): void
+    {
+        $this->db->shouldReceive('prepare')
+            ->once()
+            ->with(Mockery::pattern('/ALTER TABLE %i MODIFY offering_id .*NULL/'), 'wp_us_questions')
+            ->andReturn('ALTER TABLE `wp_us_questions` MODIFY offering_id BIGINT UNSIGNED NULL DEFAULT NULL');
+
+        $this->db->shouldReceive('query')
+            ->once()
+            ->with('ALTER TABLE `wp_us_questions` MODIFY offering_id BIGINT UNSIGNED NULL DEFAULT NULL')
+            ->andReturn(0);
+
+        // A successful DDL query returns 0 rows affected (not false).
+        self::assertTrue($this->repo->ensureOfferingNullable());
+    }
+
+    public function testEnsureOfferingNullableReportsFailureWhenQueryFails(): void
+    {
+        $this->db->shouldReceive('prepare')->once()->andReturn('ALTER ...');
+        $this->db->shouldReceive('query')->once()->andReturn(false);
+
+        self::assertFalse($this->repo->ensureOfferingNullable());
+    }
 }