Wrong binding for result variable

[mdelmans]

Looks like the right way to do result variable mapping is:

{
    "label": "Result Variable",
    "description": "Name of variable to store the response data in.",
    "value": "response",
    "type": "String",
    "optional": true,
    "binding": {
      "type": "zeebe:output",
      "source": "=response"
    }
}

Tasks should return {response: ret_value} so that zeebe can map ret_value under the response key to the variable name the user specified.