Added astronomical clock

[Mond1c]

No description provided.

[irdkwmnsb]

Why not just make the default null or undefined instead of an empty string?

[Mond1c]

But if we have such a situation: we set "timeZone" to utc. Then we set "timeZone" to an empty string. In tickerSettings "timeZone" is now equals to an empty string. So it's not null => we have InvalidDateAndTime. But we expected contest time.

We can change this part of code:

const dateTime = DateTime.now().setZone(event.target.value);
if (dateTime.isValid || event.target.value === "") {
    setErrorMessage("");
    onChangeFieldEventHandler(setEditData, "timeZone")(event);
} else {
    setErrorMessage(dateTime.invalidReason);
}

But I don't think this is a good idea, becase we need to create a new function instead of using onChangeFieldEventHandler. (This necessary for this because if event.target.value is an empty string we can change value to null).

[irdkwmnsb]

I'm talking mostly about backend behaviour here. As far as i can see this line of code just changes an empty string from the backend to a null

[Mond1c]

Okay I can do something like this:

override fun toMessage(): ClockTickerMessage {
    if (timeZone != null && timeZone.isEmpty()) {
        return ClockTickerMessage(ClockTickerSettings(part, periodMs, null))
    }
    return ClockTickerMessage(this)
} 

[Mond1c]

fixed

[irdkwmnsb]

Now there is a strange type in the typescript.
But I guess we will fix it once we (cc @kunyavskiy) figure out a way to canonize them to all be either null or undefined.