covidcast endpoint - as_of field fails silently when given a range of dates

[dshemetov]

Giving as_of a date range fails silently and it returns the latest data. Example:
https://delphi.cmu.edu/epidata//covidcast/?data_source=hhs&signals=confirmed_admissions_influenza_1d_prop_7dav&time_type=day&geo_type=state&time_values=%2A&geo_values=ca&as_of=20230101-20230102

Giving a single date gives different issues
https://delphi.cmu.edu/epidata//covidcast/?data_source=hhs&signals=confirmed_admissions_influenza_1d_prop_7dav&time_type=day&geo_type=state&time_values=%2A&geo_values=ca&as_of=20230102

Giving it a list of dates, it fails with a helpful error message:
https://delphi.cmu.edu/epidata//covidcast/?data_source=hhs&signals=confirmed_admissions_influenza_1d_prop_7dav&time_type=day&geo_type=state&time_values=%2A&geo_values=ca&as_of=20230101,20230102

[edit from katie:] The behavior we want is for it to fail with a helpful error message.

[dmytrotsko]

This happens, because time range like this -> 20230101-20230102 is a "valid range".
This function is used to parse it:

    # parses a given string in format YYYYMMDD or YYYY-MM-DD to a number in the form YYYYMMDD
    try:
        if s == "*":
            return s
        else:
            return int(s.replace("-", ""))
    except ValueError:
        raise ValidationFailedException(f"not a valid date: {s}")

Which means that 20230101-20230102 is parsed to 2023010120230102.