Immutable data

[![GitHub Workflow Status (with event)](https://img.shields.io/github/actions/workflow/status/ha0z1/idmp/deploy.yml)](https://github.com/ha0z1/idmp/actions) [![npm](https://img.shields.io/npm/v/idmp.svg)](https://www.npmjs.com/package/idmp) [![codecov](ht