CVE-2023-2780: mlflow Path Traversal vulnerability

The core vulnerability stems from two key functions: 1) _validate_source in handlers.py lacked proper file URI validation and path containment checks, as shown by the patch adding MLFLOW_ALLOW_FILE_URI_AS_MODEL_VERSION_SOURCE checks. 2) is_local_uri in uri.py had incomplete hostname validation that allowed bypasses via 127.0.0.1/localhost URIs, as evidenced by the patch adding explicit hostname checks. The commit diff shows these functions were modified to add security controls, and the CVE description explicitly references path traversal via file URIs bypassing previous fixes.