API's `user PUT` does not work as written in the API specs

[moosetwin0]

I am referring to this part of the API specs; I tried it out myself, but it only gives an http-415 error.

Here's a screenshot of the commands I sent:

I did try putting the customData as { /* your custom json here! */ }, but that gave me a syntax error. As such, I left it empty. (Which is what the specsheet recommends)