For existing customer Lead is to be converted without creating any corresponding Opportunity

Business Requirement:

To close/convert a Lead while business do not want to create an opportunity in few cases and end the Sales process journey with the Lead closure itself. This is required for the process being managed via Rest APIs to fetch and update the required leads to be closed positively i.e. similar to converted however no Opportunity is to be created in such cases.

Please guide on how this can be achieved using REST APIs or groovy or smart actions which can be invoked using Rest API.

We have observed that the Update the Lead StatusCode with "Converted" does not really update in the database as 'Converted' while we get 200 status response.