Only show Network Admin if the user is a ZC of a network

app/Models/User.php

@@ -79,4 +79,14 @@ class User extends Authenticatable implements MustVerifyEmail
 	{
 		return FALSE;
 	}
+
+	/**
+	 * Is this user a ZC of a domain?
+	 *
+	 * @return bool
+	 */
+	public function isZC(): bool
+	{
+		return $this->systems->pluck('addresses')->flatten()->where('role',Address::NODE_ZC)->count() > 0;
+	}
 }