Develop internal messaging system using Sendbird solution in React.JS

We would like to create an internal messaging system using Sendbird solution in React.JS : [URL visible pour les membres Pro]

The aim is to integrate this app into our website (already created) to allow communication between:
- A buyer and a seller.
- A buyer and an admin
- A seller and a buyer
- A seller and a group of buyers
- A seller and an admin
- An admin and a seller
- An admin and a buyer

Usage case:
--> A buyer is a connected user which has the possibility to contact a seller or an admin (for technical questions). The seller receives a notification and can answer the seller questions...
It creates a new channel if they never communicate before or it can reopened an old existing communication.
--> A seller can create a new channel to communicate with a single buyer or with a group of buyers and communicate all togethers.

The documentation is here : [URL visible pour les membres Pro]

We will provide you the webservices to call (userIds, userLists, etc...).

Requirements:
- React.JS
- Liferay 7+ (not necessary required)