User Mention with non-English(Korean) names are not pickup in suggestions when Korean typed after @...

Issue Summary

@User mentions not working in Korean language.

User ID is in the form of "English name(Korean name)/company" "ted.com(이규승)/kakao"

The Korean name to be used in the mention You can enter it as "@이규승”.

In the previous version 8.13.25, the correct user-id was suggest was started by just typing “@이”

Steps to Reproduce

1. Create a user with user name "ted.com(이규승)/kakao"
2. Make sure all permission is granted so @user mention can be used in the issue
3. Type Mention “@이” in comment
4. Jira 8.13.29 will correctly suggest the user-id when Korean characters are typed
5. Jira 8.20.11 will fail to  suggest the user-id when Korean characters are typed
6. Testing can be performed by copy/paste of strings inside double quotes

Actual Results

https://jira.atlassian.com/secure/attachment/427195/JRASERVER-74306-8.20.11.png
 

Expected Results

https://jira.atlassian.com/secure/attachment/427196/JRASERVER-74306-8.13.29.png
 

Cause of issue

May be related to:
https://jira.atlassian.com/browse/JRASERVER-74107

Workaround

none.