Add possibility to add user to the team by the platform administrator via API

### Description

As a platform administrator, I would like to have the ability to add existing users to existing teams via API.

Unfortunately, full automation of this process via API is not possible at the moment. The only way to partially achieve this is to create an invitation for the user to join a particular team. However, since admin users cannot create a Personal Access Token (PAT) for regular users and interact with the platform as these users, accepting the invitation as a regular user is not possible, and manual intervention is needed.

### Which customers would this be available to

Everyone - CE/Starter/Team/Enterprise

### Have you provided an initial effort estimate for this issue?

I can not provide an initial effort estimate