Authentication results in Error 412 (missing user data)

Hi there,

I’m trying to create a user via /api/cockpit/saveUser. But if I follow the instructions in the docs all I get is an error 412 (Precondition failed) missing user data. This is how my code looks like:

const url = `${apiBaseUrl}/api/cockpit/saveUser?token=${apiToken}`
fetch(url, {
  method: 'post',
  header: { 'Content-Type': 'application/json' },
  body: JSON.stringify({
    user: {
      name: 'Name',
      user: 'username',
      email: 'info@test.de',
      group: 'user',
      password: 'Passwort',
      api_key: 1
   }
})

})

I tryed to create a new user by Postmann with the same result?

Any hints how to handle that?