SubscribeMenuLink declares the user.roles cache context but varies per user, leaking Join/Upgrade labels across users

Fixed in the MR, in two commits, with one scope addition and one policy change worth flagging.

The menu link. SubscribeMenuLink now declares the user cache context (not user.roles) and the subscription_list cache tag, so a user's own label also flips when they subscribe. The cache_contexts key in links.menu.yml is removed: MenuLinkBase never read it, so it only documented an intention. The label strings move to a new SubscriptionManagerService::subscribeLabel(AccountInterface $account): TranslatableMarkup, which both getTitle() and the subscribe page's _title_callback use, so they cannot disagree.

Same bug, one page over. The subscribe page itself had the same class of problem: subscribe() redirects subscribers to their connector but renders the connector chooser for everyone else, and the chooser's render array declared no cache metadata while the route has no no_cache. Dynamic Page Cache would therefore have served one user's chooser page (title "Join" included) to a subscriber with the same permissions who should have been redirected. The chooser build now declares the user context and the subscription_list, subscription_plan_list and config:subscription_manager.settings tags — who sees it depends on their own subscription, what it lists on the visible plans and the chooser settings.

Autowiring, and Drupal 10. SubscribeMenuLink was pulling its dependencies through \Drupal:: calls. Since core 11.3 PluginBase::create() autowires plugin constructors (and MenuLinkDefault no longer overrides it), so the plugin now just declares a constructor with the current user and the subscription manager (the latter via #[Autowire(service: 'subscription_manager')], as the service has no interface alias). On Drupal 10 that constructor would fatal, because MenuLinkDefault::create() there still passes exactly four arguments. Rather than keep a hand-written factory for a core version that reaches end of life in about two months, alongside Drupal 12's release, core_version_requirement becomes ^11.3. Drupal 10 was nominal support anyway — nothing in this roadmap ever ran the module on it, and the CI tests only the current major. The #[LegacyHook] shims that existed for 10 can go in the cleanup omnibus (#3616937: Cleanup omnibus: dead config keys, missing token dependency, per-role user saves, page_attachments overhead, drush alias, field length, translatability, misc), along with autowiring the remaining plugins. Drupal 12 support is a separate roadmap step; 1.0.0 is realistically a Drupal 12-era release.

Tests. SubscribeMenuLinkTitleTest now builds the plugin through create() as the menu system does, and gains two cases: two users with identical roles get different labels from one link instance, which declares user (and not user.roles) and subscription_list; and the labels are TranslatableMarkup, with the page title callback agreeing with the menu link in both states. ConnectorChooserTest asserts the chooser build's contexts and tags. Suite at 164 kernel tests.

Change record drafted (the core requirement change is the user-visible part).