@type t() :: %Hyperliquid.WebSocket.Manager.Subscription{
  callback: function() | nil,
  connection_pid: pid() | nil,
  connection_type: atom(),
  id: String.t(),
  key: String.t(),
  last_message_at: DateTime.t() | nil,
  message_count: non_neg_integer(),
  message_timestamps: [DateTime.t()],
  module: module(),
  params: map(),
  subscribed_at: DateTime.t()
}