refactor(mail): make a category's owner and name non-null, and satisfy PHPStan

InboxCategory::$usr and $name are NOT NULL columns, so they are declared that
way (Message::$account is the precedent) instead of nullable with a
check nobody can reach. FilterDescriber keys its category names by the user
identifier rather than reading an id off a UserInterface, which adds nothing
to the baseline. Test fixtures stop storing threads they never read back.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

src/Entity/Mail/InboxCategory.php

@@ -50,10 +50,10 @@ class InboxCategory
 
     #[ORM\ManyToOne]
     #[ORM\JoinColumn(nullable: false, onDelete: 'CASCADE')]
-    public ?User $usr = null;
+    public User $usr;
 
     #[ORM\Column(length: self::NAME_MAX_LENGTH)]
-    public ?string $name = null;
+    public string $name;
 
     /** Left to right among the user's own tabs; ties break on id. */
     #[ORM\Column(options: ['default' => 0])]

src/Service/Mail/InboxCategoryManager.php

@@ -63,13 +63,7 @@ final readonly class InboxCategoryManager
      */
     public function rename(InboxCategory $category, string $name): void
     {
-        $owner = $category->usr;
-
-        if (null === $owner) {
-            throw new \LogicException('A category with no owner cannot be renamed.');
-        }
-
-        $category->name = $this->validName($owner, $name, $category);
+        $category->name = $this->validName($category->usr, $name, $category);
 
         $this->em->flush();
     }
@@ -113,7 +107,7 @@ final readonly class InboxCategoryManager
                 continue;
             }
 
-            if (mb_strtolower((string) $existing->name) === mb_strtolower($name)) {
+            if (mb_strtolower($existing->name) === mb_strtolower($name)) {
                 throw new InvalidInboxCategoryException('settings.categories.error.taken');
             }
         }

src/Service/Rule/FilterDescriber.php

@@ -41,7 +41,7 @@ final class FilterDescriber implements ResetInterface
     /** @var array<int, array<int,string>> userId => (integrationId => name) */
     private array $integrationNames = [];
 
-    /** @var array<int, array<int,string>> userId => (categoryId => name) */
+    /** @var array<string, array<int,string>> user identifier => (categoryId => name) */
     private array $categoryNames = [];
 
     /** Whose labels the sentence currently being built may name. */
@@ -311,13 +311,15 @@ final class FilterDescriber implements ResetInterface
             return $missing;
         }
 
-        $userId = (int) $this->subject->id;
+        // Keyed by the user identifier rather than by an id: all that is known
+        // here is a UserInterface, which has no id to read.
+        $userId = $this->subject->getUserIdentifier();
 
         if (false === array_key_exists($userId, $this->categoryNames)) {
             $map = [];
 
             foreach ($this->categoryRepository->findForUserOrdered($this->subject) as $category) {
-                $map[(int) $category->id] = (string) $category->name;
+                $map[(int) $category->id] = $category->name;
             }
 
             $this->categoryNames[$userId] = $map;

tests/Repository/Mail/InboxTabQueriesTest.php

@@ -59,11 +59,6 @@ final class InboxTabQueriesTest extends KernelTestCase
     private Label $inbox;
     private InboxCategory $shipping;
 
-    private MessageThread $carrierNew;
-    private MessageThread $promoNew;
-    private MessageThread $primaryRead;
-    private MessageThread $updateRead;
-
     protected function setUp(): void
     {
         self::bootKernel();
@@ -85,10 +80,10 @@ final class InboxTabQueriesTest extends KernelTestCase
         $this->em->persist($this->shipping);
         $this->em->flush();
 
-        $this->carrierNew  = $this->inboxThread('carrier, new', MessageCategory::Promotions, $this->shipping, unread: 1);
-        $this->promoNew    = $this->inboxThread('promo, new', MessageCategory::Promotions, null, unread: 1);
-        $this->primaryRead = $this->inboxThread('primary, read', MessageCategory::Primary, null, unread: 0);
-        $this->updateRead  = $this->inboxThread('update, read', MessageCategory::Updates, $this->shipping, unread: 0);
+        $this->inboxThread('carrier, new', MessageCategory::Promotions, $this->shipping, unread: 1);
+        $this->inboxThread('promo, new', MessageCategory::Promotions, null, unread: 1);
+        $this->inboxThread('primary, read', MessageCategory::Primary, null, unread: 0);
+        $this->inboxThread('update, read', MessageCategory::Updates, $this->shipping, unread: 0);
     }
 
     protected function tearDown(): void

tests/Service/Imap/MessageThreaderTest.php

@@ -147,10 +147,10 @@ final class MessageThreaderTest extends TestCase
 
         $this->threaderWithThreadLookup(null)->assignThread($message, new Account());
 
-        self::assertSame($shipping, $message->thread?->userCategory);
+        self::assertSame($shipping, $message->thread->userCategory);
         self::assertSame(
             MessageCategory::Promotions,
-            $message->thread?->category,
+            $message->thread->category,
             'the built-in category must still be the one the rules decided',
         );
     }

tests/Service/Mail/InboxTabsTest.php

@@ -70,7 +70,7 @@ final class InboxTabsTest extends TestCase
         $tabs = new InboxTabs($repository);
 
         self::assertSame('c12', $tabs->resolve($this->user('reader'), 'c12')?->value);
-        self::assertSame('Shipping', $tabs->resolve($this->user('reader'), 'c12')?->name);
+        self::assertSame('Shipping', $tabs->resolve($this->user('reader'), 'c12')->name);
         self::assertNull($tabs->resolve($this->user('stranger'), 'c12'), 'resolved a category the asking reader does not own');
     }
 

tests/Service/Rule/RuleCategoryFilerTest.php

@@ -67,7 +67,7 @@ final class RuleCategoryFilerTest extends TestCase
         self::assertSame($this->shipping, $message->thread?->userCategory);
         self::assertSame(
             MessageCategory::Promotions,
-            $message->thread?->category,
+            $message->thread->category,
             'filing must leave the built-in category alone: JMAP clients are served it',
         );
     }