Use this to set the test cycle's custom fields.

The value should be a JSON object where the keys are the test cycle custom field name and the values are the respective custom field values.

Here's an example:

        {
            "single-choice": "option1",
            "checkbox": true,
            "userpicker": "5f8b5cf2ddfdcb0b8d1028bb",
            "single-line": "a text line",
            "datepicker": "2020-01-25",
            "decimal": 10.55,
            "number": 50,
            "multi-choice": ["choice1","choice2"],
            "multi-line": "first line<br />second line"
        }
    


If there's a parsing error while parsing the JSON, the value will be ignored and this field will then be empty upon page reload.