Error in trying to create environment via Cloud REST API

I am attempting to create a new environment via the REST API using this documentation. The example request body in that example doesn’t make sense so I’ve attempted to construct it using minimum requirements. My 1st attempt was just to supply a name in the body but I got a 400 response with the body of:

{
    "key": "deploy-service.request.validation-error",
    "message": "The request body contains invalid properties",
    "arguments": {
        "environment.environment_type": "Property environment_type is required"
    }
}

I did a GET request to retrieve current environments & noticed that property is an object like below:

{
    "page": 1,
    "values": [
        {
            "type": "deployment_environment",
            "name": "Test",
            "slug": "test",
            "rank": 0,
            "environment_type": {
                "type": "deployment_environment_type",
                "name": "Test",
                "rank": 0
            }
      }
  ]
}

I then set my request body to be:

{
    "name": "foobar",
    "environment_type": {
        "type": "deployment_environment_type"
    }
}

(type is just mirroring what I got in the response to GET an environment). This returns a 500 saying it’s unable to process the request. If I set this to a string instead of an object, I’m returned with a 400 response saying that the JSON is unable to be processed.

I imported the swagger documentation into Postman & this doesn’t even have the key of environment_type in the request body &, thus, fails. I’m very uncertain how to go about this & am not finding the documentation particularly useful.