Create a custom field value

{
	"accountCustomFieldDatum": {
		"accountId": "2",
		"customFieldId": "1",
		"fieldValue": "test title"
	}
}

{
    "accountCustomFieldDatum": {
        "id": "5",
        "accountCustomFieldMetumId": 1,
        "accountId": 2,
        "customFieldId": 1,
        "createdTimestamp": "2018-11-06 02:27:05",
        "updatedTimestamp": "2018-11-06 02:27:05",
        "fieldValue": "test title",
        "links": {
            "account": "https://:account.api-us1.com/api/:version/accountCustomFieldData/5/account",
            "accountCustomFieldMetum": "https://:account.api-us1.com/api/:version/accountCustomFieldData/5/accountCustomFieldMetum"
        }
    }
}