[extracted from `data_loader`] broke out log parsing implementation from data processing class
[extracted from `data_loader`] broke out log parsing implementation from data processing class

wikimedia/user_metrics,wikimedia/user_metrics,wikimedia/analytics-user-metrics,rfaulkner/wikipedia_user_metrics,wikimedia/user_metrics,rfaulkner/wikipedia_user_metrics,wikimedia/analytics-user-metrics,rfaulkner/wikipedia_user_metrics,wikimedia/analytics-user-metrics