Entity union / extending types in the same subgraph?

Help
,
1

We have a lot of subgraphs, most of them pretty small where we make use of the entity unions / extending entities across subgraphs. However I have one small case where I am looking for a solution on how to do the same but in the same subgraph, is this even supported?

Here is my entity:

type Chat @key(fields: "id") {
  id: ID!
  listingId: String!
  createdAt: DateTime!
  updatedAt: DateTime!
  participants: [Participant!]!
  title: String!
}

I would like to be able to extend the above with:

  id: ID!
  chatId: String!
  content: String!
  createdAt: DateTime!
  participant: Participant!
}

extend type Chat @key(fields: "id") {
  id: ID!
  messages: [Message!]!
}

The reason I want this is because I don’t want the messages always resolved in the resolver, only on demand. Is there a better solution other than moving the messages to it’s own subgraph?

I am using node.js apollo-server.