To update multiple users at once, you can use the same request as add customer and just add other users in request JSON body separated by commas:
[
{
"user_id": "123",
"name": "Ivan Dobsky",
},
{
"user_id": "124",
"name": "Jane Doe",
},
{
"user_id": "125",
"name": "John Doe",
}
]