No notification sent when customer share issue

Issue Summary

Customers do not receive notifications when they are added to "Share (Request participant)" in the service desk portal.

Steps to Reproduce

1. Create a service desk issue
2. View the issue from the portal.
3. Share the issue with a customer

Expected Results

A notification that they've been added as a participant to the ticket is sent to the customer

Actual Results

No notification is sent to the customer

Workaround

Currently none