Input data - Date information

[LucieContamin]

From Issue #1

Arguments specifying input data
forecast_data required data.frame with forecasts in the hub_mdl_out_df format. Noting that maybe we want to start by supporting only certain output types (e.g. quantiles, means, medians, maybe samples once we implement
All forecasts in forecast_data will be plotted, i.e. all filtering needs to happen outside this function. We note per validation specified below that this data.frame must have either a target_date column of both of a origin_date and horizon column.

Currently, the input data is required to have a target_date column, it would be interesting the add the capacity to have input file with origin_date and horizon , with the associated formula and have the capacity to calculate the target_date column if missing.