fix: fix frequency_to_string outputing 108000s

[floriankrb]

Description

Fixes #215

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[anaprietonem]

Changes looks good, and assert confirm it's working as expect. I think the function could be simplified as right now there is a renaming from total_seconds to second that looked unnecessary. If this function is just experimental feel free to ignore, if we plan to use this across packages I think cleaning could then be added.

def frequency_to_string(frequency: datetime.timedelta) -> str:
    total_seconds = int(frequency.total_seconds())
    if total_seconds < 0:
        return f"-{frequency_to_string(-frequency)}"

    if total_seconds % (24 * 3600) == 0:
        return f"{total_seconds // (24 * 3600)}d"
    elif total_seconds % 3600 == 0:
        return f"{total_seconds // 3600}h"
    elif total_seconds % 60 == 0:
        return f"{total_seconds // 60}m"
    else:
        return f"{total_seconds}s"

[anaprietonem]

thanks for the changes @floriankrb, good to be merged!