Unable to add new users to a group

From the user groups pages (#/2/settings/usergroups), I am trying to add an user to an existing group.

A call is made to /rest/api/2/user/search?maxResults=10&startAt=0&username=<search_query> and the response is:

  "errorMessages": [
    "The query parameter 'username' is not supported in GDPR strict mode."
  "errors": {}

The suggested fix it to use query instead of username as the query parameter.

Eg. /rest/api/2/user/search?maxResults=10&startAt=0&query=<search_query>

See https://community.atlassian.com/t5/Jira-questions/The-query-parameter-username-is-not-supported-in-GDPR-strict/qaq-p/1345106