Refactor more old code and get tests to pass

src/Database/Concerns/PrimaryDomain.php

@@ -0,0 +1,17 @@
+<?php
+
+namespace Stancl\Tenancy\Database\Concerns;
+
+/**
+ * @property-read string $primary_domain_hostname
+ */
+trait PrimaryDomain
+{
+    // This string should usually come from a relationship implemented by you.
+    abstract public function getPrimaryDomainHostnameAttribute(): string;
+
+    public function route($route, $parameters = [], $absolute = true)
+    {
+        return tenant_route($this->primary_domain_hostname, $route, $parameters, $absolute);
+    }
+}