fix some issues

Signed-off-by: Maurice Preuß (envoyr) <hello@envoyr.com>

src/Id/Concerns/HasBillable.php

@@ -2,21 +2,18 @@
 
 namespace Anikeen\Id\Concerns;
 
-use Anikeen\Id\Contracts\Billable;
-use Illuminate\Database\Eloquent\Model;
-
 trait HasBillable
 {
-    protected Billable|Model $billable;
+    public mixed $billable;
 
-    public function setBillable(Billable|Model $billable): self
+    public function setBillable(mixed $billable): self
     {
         $this->billable = $billable;
 
         return $this;
     }
 
-    public function getBillable(): Billable|Model
+    public function getBillable(): mixed
     {
         return $this->billable;
     }