Performs a bulk update of user group assignments.

This endpoint performs a bulk update of user group assignments, making it easier to manage group membership for multiple users efficiently.</br></br>Key features include:</br></br>- Clear success messaging: Returns a 204 success code with a confirmation message indicating the successful completion of the requested action.</br>- Comprehensive error handling: Returns 400 and 404 error codes with clear descriptions when requests fail.</br>- Reliable user group updates: Facilitates the bulk modification of user groups, ensuring accurate and up-to-date information across the system.