Facebook provides users with various ways to interact. Currently, we only have the opportunity to request and insert posts. As in the case of Facebook, we want to have chats with our friends and colleagues. We will introduce two new entities to cover this.

The first entity is called Chat, and the second is called Message.

Before starting with the implementation, we need to lay out a detailed plan of what those entities will enable us to do.

A user can have multiple chats, and a chat can belong to multiple users. This relationship gives us the opportunity to have group chats with multiple users, as well as private chats, between only two users. A message belongs to one user, but every message also belongs to one chat.