message: Add error trace on casting SovrinError to ErrorCode.
diff: @@ -60,6 +60,7 @@ impl error::Error for SovrinError {
  impl ToErrorCode for SovrinError {
  fn to_error_code(&self) -> ErrorCode {
  + error!("Casting error to ErrorCode: {}", self);
  match *self {
  SovrinError::AnoncredsError(ref err) => err.to_error_code(),
  SovrinError::CommonError(ref err) => err.to_error_code(),
  