feat: harmonize mailbox list and track harmonization state

Signed-off-by: Sebastian Krupinski <krupinski01@gmail.com>

lib/Providers/Service.php

@@ -237,6 +237,11 @@ class Service implements ServiceBaseInterface, ServiceMutableInterface, ServiceC
         return $this->serviceIdentifier;
     }
 
+    public function tenantIdentifier(): ?string
+    {
+        return $this->serviceTenantId;
+    }
+
     public function getLabel(): ?string
     {
         return $this->serviceLabel;