In the proposal modules we need to implement mapping from the Substrate origin parameter in extrinsics to the actor_id.

For example in the create_proposal API call, actor_id is proposer_id:

        let account_id = T::ProposalOrigin::ensure_origin(origin)?;
        let proposer_id = T::ProposerId::from(account_id.clone());

We need to implement these conversions in the engine module for ProposerId and VoterId and in the discussion module for the ThreadAuthorId and PostAuthorId.