Add branch permission restrictions via REST API

https://docs.atlassian.com/bitbucket-server/rest/7.4.0/bitbucket-ref-restriction-rest.html.
Under this, I refer POST method of /rest/branch-permissions/2.0/projects/{projectKey}/repos/{repositorySlug}/restrictions

I am able to use this API successfully. I see that if the rule doesn't exist, it creates it.
However, if the rule already exist with certain list of users, instead of appending new users to the rule it removes existing users & add new users specified in my rest api.

This feature request is to provide a PUT method to add to the existing rules rather than replacing them.