Filename convention incompatibility

Modeler Instructive S1.3 gives two options:

• long version: contain both start & end dates (date & time component in isoformat);
• short version (only for whole-day forecasts): only the start date

Since commit 86534036, pymock's forecast filenames (libs.syncat_path) contain both the start & end dates and drop the time component if both refer to midnight, but this causes incompatibility with S1.3:

• for the long version: the time is not included
• for the short version: the end date is included

Suggested solution (for the instructive and pymock)

The CSEP Italy Experiment only foresees whole-day forecasts as stated in section 2.4: "1-day intervals, [...] starting at midnight". So I very much like the short version as the go-to solution, because:

• dropping the end date is justified by the experiment defining/fixing the forecast interval;
• dropping the time if it is always 00:00:00 is elegant and gives easy digestible filenames. Only if the experiment foresees some irregular forecast updates during the day, the time component should be included - even for midnight forecasts for consistency & reduced file writer/reader complexity.

So there should be no need for the long version at all.

Specifically for libs.syncat_path I'd restore the previous version:

def syncat_path(date, folder):
    if isinstance(date, str):
        date = datetime.fromisoformat(date)
    return os.path.join(folder, f'pymock_{date.date().isoformat()}.csv')

(Remove .date() if irregular forecast updates may indeed occur.)