Updating or deleting a customer account does not send "user_updated" or "user_deleted" webhooks

Issue Summary

Jira webhooks for "user_updated" and "user_deleted" events don't fire if a JSD customer account user is updated or deleted in user management.

Steps to Reproduce

1. Create a JSD customer account, such as in a JSD project: go to Customers > Add customers and add a new customer
2. Create a webhook in Jira global administration, listening to all the user related events (created, updated, deleted). You can use a tool like "request catcher" to show the requests that come through.
3. Go to settings > user management (site administration) > Jira Service Desk
4. Edit the full name of a customer

Expected Results

A "user_updated" webhook event is published.

Actual Results

No event is published for the updated user.

Workaround

Periodically re-fetch customer information using the JSD Cloud REST API.