fix: user query parameter must include username [DHIS2-18748]

[jbee]

Summary

When using the query parameter with User this should not run the standard implementation.
Therefore query needs to be considered a "special filter" and excluded for users.

This got overlooked when reworking the special filters in #19046 since the query parameter basically has a name clash.

Manual Testing

Using it to find system user by username once with other special filters and once without

• /api/users?userOrgUnits=true&includeChildren=true&query=system
• /api/users?query=system
• check both URLs result in a list containing the system user (in SL this is the only match)

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[david-mackessy]

Can a test be added for this fix?