Migration-planner: credentialurl validator accepts javascript: urls

A flaw was found in migration-planner. Insufficient validation of the `AgentStatusUpdate.CredentialUrl` field allows an authenticated attacker to store a malicious `javascript:` URL. When a victim views this URL in the Hybrid Cloud Console, it can lead to Cross-Site Scripting (XSS), enabling script execution in the victim's session and potentially disclosing sensitive information.