Forced local Unix socket connection via dot-sock KMS endpoint in client-side field encryption

The client-side field level encryption support in the MongoDB Python Driver can treat a key management endpoint value ending in ".sock" as a local Unix domain socket path rather than a remote host. A user with write access to the encryption key metadata stored in the database can cause an application using the driver to open connections to local sockets on the application host. Data sent over these connections is limited to the start of a TLS handshake, so no chosen content is transmitted.