Designing schema for chat system in AWS Amplify

Question

I am designing a chat system. I want to have this relational model but not sure how to configure the schema in datastore. A user can have many conversation and a conversation can have many users. I have setup a schema but it doesn't let me attach many users to a conversation. This is my current schema but as you can see, the UserConversation class doesn't let me add multiple users to it. The idea is that when I query a user, I want to be able to fetch all the conversations they are in but a conversation will need to have more than 1 person but according to schema I can only link 1 user to the relation. How do I achieve what I want.

This is my attempt of schema but it doesn't seem to work.

type User @model @auth(rules: [{allow: public}]) {
  id: ID!
  Conversations: [Conversation] @manyToMany(relationName: "UserConversation")
}

type Conversation @model @auth(rules: [{allow: public}]) {
  id: ID!
  users: [User] @manyToMany(relationName: "UserConversation")
}

class UserConversation extends Model {
  static const classType = const _UserConversationModelType();
  final String id;
  final Conversation? _conversation;
  final User? _user;

  // Other class methods
}