Hi,
First i would see if i can set the contact type on creation of the record from the widget itself.
Because you would be using the out of the box scripted rest api to create the item and you should be able to set it via the widget itself.
As an alternative,
I would use something like the way Track approval source Business rule works on Approval table.
So i would create the following script in my widget before the creation of the request
var controller = new GlideController();
controller.putGlobal("contact_type", "self-service");
After creation of the request please clear the global value
controller.removeGlobal("contact_type");
In my sc_Req_item, i will have a business rule on insert which will check for contact_type and update it on the record
var controller = new GlideController();
var contact_type = controller.getGlobal("contact_type");
