Add support for optional fields in JIRA action "Update issue status"

In JIRA, it is possible to update fields while making a transition (where the available fields to update depend on the screen attached to the transition).

This is currently not supported in Workato so I opened this enchancement, and I've set it as Low priority since I can work around it with a custom action.

The request body will look similar to this:

```

{

    "fields": {

        "customfield_12345": [

            "label-value"

        ],

        "customfield_12321": "stringValue"

    },

    "transition": {

        "id": 123

    }

}

```

More documentation available at