how to add custom validation and message in laravel nova for one field

I want to add custom validation for one field in laravel nova resouce file.

I have one field in db which is service_id in the service table and i have nova resource file for the same table, on create service I want to get data using service_id from other table and check data is present or not and if present then i don't want to enter that service_id in table.

so can someone help me how can I write custom validation rules in laravel nova resource file?

via Chebli Mohamed