Notification emails for form submissions do not contain the "From:" header.
This is bad practice and causes email sending to fail silently on Platform.sh (likely other places too)

This is because Platform.sh uses SendGrid and SendGrid requires the From header to exist

The problem is in this code:
https://github.com/ezsystems/ezplatform-form-builder/blob/master/src/lib/FormSubmission/Notification/EmailNotificationSender.php#L80-L91

Not sure where we should store the From: email address.
This could possible be set via GUI in form creator as I easily can see the need for having it differently per form?

or we could use the existing 'app.contact_form.sender_email' parameter, create a new parameter or use the swiftmail setting 'sender_address'