Build a NodeJs + Express + MongoDB backend for existing React frontend => MERN stack -- 2

There is a messenger that is very similar to Slack, called Mattermost ([login to view URL]). In it we have 1. a React frontend ([login to view URL]) 2. a mobile component for iOS and Android ([login to view URL]) 3. a desktop component for Windows/Mac/Linux ([login to view URL]) and 4. a Redux component of which make heave use throughout ([login to view URL]) Furthermore, we have a documentation here: [login to view URL] In the current situation we have a backend written in Go ([login to view URL]) with Postgresql as database. We intend now to rewrite the backend with NodeJs + Express + MongoDB. Hence, it would be your task to take the current Frontend part is it is right now (Points 1-4) and to write a new backend from scratch, such that we have a functioning MERN stack, such that we can make use of it for both Browser frontend, Mobile apps and [login to view URL] function should cover all the functionalities that are already present in mattermost-server ([login to view URL]). Furthermore, for using text search we should use Elasticsearch. This can be done by syncing Elasticsearch and MongoDB with a connector (for instance, with [login to view URL]) and if someone makes a search now, he will search via Elasticsearch. All components should be dockerized and we should be able to test everything via docker-compose. Also tests for all components would have to be included for all components like APIs, for instance, with Mocha and Chai.