Internal function to prepare data for plotting or returning merged predictions and observations. Combines predictions with observed data from each snapshot, including the latest observations as reference.
merge_trunc_pred_obs(observations, predictions)A <data.table> with columns: date, report_date, confirm (observed),
last_confirm (from latest snapshot), and prediction columns (median, CrIs).
A list of <data.frame>s containing date and confirm
columns, as stored in an estimate_truncation object.
A <data.table> of predictions from get_predictions().