Mask underlying errors in TransactionOperationFailed

When we return a TOF to the user then we return the underlying error cause when Unwrap is used. We have an issue that if we return errors like doc not found or doc exists for a situation where the doc involved is actually ancillary to the transaction then the user could catch it and it won't be doing what they expect. TOF is meant to be opaque anyway so we should mask the underlying error and in the case of doc not found return that error directly when applicable.