Determine caller in Installable Script - forms

Question

I've create an installable script which creates forms on the fly for 2 to 3 party verification. Since these forms are filled out asynchronously, and often in batches, it is important to determine which form called the function.
First the response form is created, then a trigger is installed.
CreateForm function:
function createForm(title){
var form = FormApp.create(title)
//set parameters for new form
form.setCollectEmail(true);
form.setShowLinkToRespondAgain(false);
...
return form;
};
InstallTrigger function:
function InstallTrigger(form, funct) {
var trigger= ScriptApp.newTrigger(funct)
.forForm(form)
.onFormSubmit()
.create()
return trigger.getUniqueId();
};
During the initial form submit, a function called createMessage() creates an email based on responses and runs the two scripts above. The email contains a link to the newly created form to await approval. To that point, everything works fine.
The problem comes when the newly installed trigger fires. I haven't found a way to set the trigger source as a variable. I'm sure that it has to do with an event, but the documentation on events doesn't go too far into forms from what I can see. I read that it can be done (Understanding Events). I just don't quite understand where (e) is defined on an installable script. Would it be in the install function or some other place?

Answer 1

Thanks again Serge inas for the walkthrough.
(e) is defined when the function defined. In my example above, the InstallTrigger() function adds a trigger to the form passed to it. The script that executes on submission is also passed to it. So, the installation of the trigger comes from a pre-installed onSubmit() trigger. In the submission function, it calls
var NewForm = FormApp.createForm();
InstallTrigger(NewForm, triggerFunction);
The function "triggerFunction" should look something like this:
function triggerFunction (e) {
Logger.log(JSON.stringify(e))
GmailApp.sendEmail("yourEmailString","Debugging",Logger.getLog() //sends an email to you with the logfile.
var form = FormApp.openByUrl(e.response.getEditResponseUrl());
...
}
The e.source mentioned in the aforementioned article says that it works for installable triggers, but when enumerated, only the e.resource and e.authMode were available. Fortunately, the e.response contains the method editUrl that can be used with the method .openByUrl() and return the original form.