Sign transactions by Clef via REST API

We should be able to sign transaction by Clef via REST API. When this feature will be in place we can completely skip signing via geth with account lock/unlock feature (unsecure).

Clef API reference: https://geth.ethereum.org/docs/tools/clef/apis

QUESTION: can we communicate with clef via IPC sockets?

NOTE: Also consider the possibility to use clef via command line.