Function apply_local_by 

pub fn apply_local_by(
    doc: &mut AutoCommit,
    action: &dyn Action,
    encoded: EncodedAction,
    actor: Option<&[u8]>,
) -> Result<ActionEnvelope, ActionError>

apply_local, attributing the resulting change to actor: the Automerge change commits under their actor so the room’s history names them the way it names a typing person. None keeps the ActionId-derived actor, as before.

Errors

See apply_local.