Searching for a user using email address in Request Participant doesn't work

Issue Summary

Searching for a user using email address in Request Participant field doesn't work. Previous FR:

• https://jira.atlassian.com/browse/JSDCLOUD-8834

Steps to Reproduce

1. Open an issue from Agent view (not portal)
2. Search for existing JSM customer using their email address

Expected Results

The user is returned from the search

Actual Results

The user is Not returned from the search

Workaround

Use their display name to search

Notes

This bug ticket is used to track an issue with the "Request participant" field. For the issue with "Reporter" field, please have a look at https://jira.atlassian.com/browse/JRACLOUD-82450