Anyone or anything that takes part in a room: a user, an admin, a guest, a service, an agent. Issho never assumes your schema; implement this protocol for each struct that can join.

defimpl Issho.Actor, for: MyApp.Accounts.User do
  def key(user), do: "user:#{user.id}"
  def display(user), do: %{name: user.name, avatar: user.avatar_url, kind: :human}
end

defimpl Issho.Actor, for: MyApp.Agents.Agent do
  def key(agent), do: "agent:#{agent.id}"
  def display(agent), do: %{name: agent.name, kind: :agent}
end

key/1 is the actor's identity in every room: namespace it, so that admin 4 is not user 4. Two tabs of one actor share a key, and others see one person.

display/1 is what the other people in a room see, so give it only what they may see: :name, :avatar (an image's URL), :color (a CSS colour) and :kind (:human, :agent or :service, :human unless given). Issho checks the colour before it reaches anyone's browser.

Maps with an :id work without an implementation, for scripts and tests: %{id: 4, name: "Ada"} is the actor "4".