feat(notifications): implement tenant-scoped broadcast notifications (EC-200)

* feat(notifications): implement tenant-scoped broadcast notifications

* refactor: move tenant related code into core package

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Co-authored-by: Omer Sabic <omer@datalinx.si>

Author: KilianTrunk

routes/channels.php

@@ -3,6 +3,7 @@
 use Eclipse\Core\Models\User;
 use Illuminate\Support\Facades\Broadcast;
 
-Broadcast::channel('Eclipse.Core.Models.User.{id}', function (User $user, $id) {
-    return (int) $user->id === (int) $id;
+Broadcast::channel('Eclipse.Core.Models.User.{id}.tenant.{tenantId}', function (User $user, $id, $tenantId) {
+    return (int) $user->id === (int) $id
+        && $user->sites()->whereKey($tenantId)->exists();
 });