Kolibri has Unauthenticated Server-Side Request Forgery (SSRF) in RemoteFacilityUserViewset

Kolibri is an offline-first education platform. Prior to version 0.19.4, several Kolibri API endpoints accept an unvalidated `baseurl` parameter and fetch attacker-controlled URLs from the Kolibri server, reflecting the response body back to the caller. The original report identified two endpoints on the `RemoteFacilityUser*` viewsets; remediation review found two further reflection points on the same pattern. The GET endpoint was unauthenticated. Version 0.19.4 fixes the vulnerability.