Updates a custom object record. The properties of the custom object record can be updated by providing the properties field. Each key in the properties field must be a valid custom property key for the custom object, in case of an invalid key, the key will be ignored. The value of each key in the properties field must be a valid value for the custom property, in case of an invalid value, an error will be returned. In case a null value is provided for a custom property, the value of the custom property will be set to null, unless the custom property is required. If an attempt is made to set a required custom property to nil an error will be returned. In case the custom object record has properties which are not present in the update payload, those properties will not be changed.