message: Add some basic headerdoc explaining how state changes and errors are communicated.
diff: @@ -73,7 +73,21 @@ private:
  friend void unsubscribe(Subscription&);
  };
  +/// Create a partial sync subscription from the query associated with the `Results`.
  +///
  +/// The subscription is created asynchronously.
  +///
  +/// State changes, including runtime errors, are communicated via notifications
  +/// registered on the resulting `Subscription` object.
  +///
  +/// Programming errors, such as attempting to create a subscription in that is not
  +/// partially synced, or subscribing to an unsupported query, will throw an exception.
  Subscription subscribe(Results const&, util::Optional<std::string> name);
  +
  +/// Remove a partial sync subscription.
  +///
  +/// The operation is performed asynchronously. Completion will be indicated by the
  +/// `Subscription` transitioning to the `Invalidated` state.
  void unsubscribe(Subscription&);
  // Deprecated
  