/// <summary>
/// Gets a unique identifier for the current user
/// </summary>
/// <param name="application">The application for which the client ID should be retrieved</param>
/// <returns>Returns the unique identifier representing the currently active user</returns>
/// <remarks>
/// Each client ID is unique to a computer, user account, <see cref="ITrackingApplication"/>, <see cref="TrackingEngine"/> and
/// tracker ID given by <see cref="GetTrackerID()"/> (provided that the <see cref="CreateNewClientID"/> function returns
/// unique values).
///
/// If a client ID is not found for the current combination of the above then one will be generated by making a call to
/// <see cref="CreateNewClientID"/>.
/// </remarks>
protected async Task <string> GetClientIDAsync(ITrackingApplication application)
{
var clientIDKey = string.Format("{0}:{1}:{2}", this.GetType().FullName, application.Name, GetTrackerID());
return(await KeyStore.GetOrFetchObject <string>(clientIDKey, () => CreateNewClientIDAsync(application)).FirstAsync());
}
