chore: support elysia 0.7

[amokio]

I believe only one subscription per Client is supported before, and only work for single client.

example:

client1 -> subscribe -> test {id: 1, method: "subscription",…}
client1 -> subscribe -> test2 {id: 2, method: "subscription",…}
client2 -> subscribe -> test {id: 1, method: "subscription",…}
client2 -> subscribe -> test {id: 2, method: "subscription",…}

Client2 will override Client1 Unsubscribable object.
observers { 1: Unsubscribable, 2: Unsubscribable }, Here may have memory leak and the observer still listener on event emitter.

proposed data structure :

{
  "[socket.id]": { "[id]": Unsubscribable }
}