Add function for getting client's user info (#412)

lib/kino/bridge.ex

@@ -219,15 +219,26 @@ defmodule Kino.Bridge do
 
       * `{:client_leave, client_id}`
 
-  When the monitor starts and there are already clients that joined,
-  the join message is going to be delivered for each of them right
-  away.
+  Returns a list of client ids that are already joined.
   """
-  @spec monitor_clients(pid()) :: :ok | {:error, request_error()}
+  @spec monitor_clients(pid()) :: {:ok, list(String.t())} | {:error, request_error()}
   def monitor_clients(pid) do
     with {:ok, reply} <- io_request({:livebook_monitor_clients, pid}), do: reply
   end
 
+  @doc """
+  Returns user information for the given connected client id.
+
+  Errors with `:not_available`, unless the notebook uses a Livebook
+  Teams hub.
+  """
+  @spec get_user_info(String.t()) ::
+          {:ok, Kino.Hub.user_info()}
+          | {:error, :not_available | :not_found | request_error()}
+  def get_user_info(client_id) do
+    with {:ok, reply} <- io_request({:livebook_get_user_info, client_id}), do: reply
+  end
+
   @doc """
   Checks if the caller is running within Livebook context (group leader).
   """

lib/kino/hub.ex

@@ -31,4 +31,26 @@ defmodule Kino.Hub do
       {:error, _} -> %{type: :none}
     end
   end
+
+  @doc """
+  Returns user information for the given connected client id.
+
+  Note that this information is only available when the session uses
+  Livebook Teams hub, otherwise `:not_available` error is returned.
+
+  If there is no such connected client, `:not_found` error is returned.
+  """
+  @spec user_info(String.t()) :: {:ok, user_info()} | {:error, :not_found | :not_available}
+  def user_info(client_id) do
+    case Kino.Bridge.get_user_info(client_id) do
+      {:ok, user_info} ->
+        {:ok, user_info}
+
+      {:error, reason} when reason in [:not_found, :not_available] ->
+        {:error, reason}
+
+      {:error, reason} ->
+        raise "failed to access user info, reason: #{inspect(reason)}"
+    end
+  end
 end