AppSync / Apollo - Subscription - Update nested array within a model - apollo-client

Question

For a Chat app I am trying to update the Apollo cache for a nested array, so that when a message is received for any conversation, the user can see the latest message in real time.
I have the following AppSync schema.
type Conversation
#model
#auth(rules: [
{ allow: owner, ownerField: "users", operations: [create, read, delete, update] }
{ allow: private, provider: iam, operations: [read, create, update, delete] }
]) {
messages: [Message] #hasMany(indexName: "messagesByConversation", limit: 1)
users: [String]
createdAt: AWSDateTime
updatedAt: AWSDateTime
}
type Message
#model(mutations: { create: "createMessage", update: "updateMessage" })
#auth(rules: [
{ allow: groups, groups: ["Users"] }
{ allow: owner, operations: [read, create, update], ownerField: "users" }
{ allow: private, provider: iam }
]) {
conversationId: ID! #index(name: "messagesByConversation", sortKeyFields: ["createdAt"], queryField: "messagesByConversation")
text: String
users: [String]!
receiver: ID!
sender: ID!
createdAt: AWSDateTime!
updatedAt: AWSDateTime
}
type Subscription {
onCreateMessageForSenderUser(sender: String!): Message #aws_subscribe(mutations: ["createMessage"])
onCreateMessageForReceiverUser(receiver: String!): Message #aws_subscribe(mutations: ["createMessage"])
}
Which has the nested model messages: [Message]
In the Apollo Cache, I can see a new typename is created called __ ModelMessageConnection to facilitate the connection
I have a subscription that listens for new messages (in this case when my user is the sender).
The trouble I am facing, is how can I update the cache so when the subscription for a new message is received, it updates for the conversation (the ModelMessageConnection)
const { data: senderMessageData } = useSubscription(
gql(SENDER_MESSAGE_SUBSCRIPTION),
{
skip: !subData?.sub,
variables: {
sender: subData?.sub
},
onSubscriptionData: (options) => {
options.client.cache.modify({
//TODO: do something here?
});
}
}
);