feat(datastore): support civil package types save

[IlyaFaer]

Support saving properties of civil package types: Date, Time and DateTime.

Closes #3089

[tritone]

Do we need to make changes to load as well?

[tritone]

FYI @BenWhitehead @crwilcox

[tbpg]

LGTM. Let's make sure to have a user test with a pseudo-version before tagging a release. Please wait for @tritone.

[tritone]

Looks good to me. @crwilcox @BenWhitehead could you please take a look before we merge?

[crwilcox]

What is the experience for someone who doesn't have civil?

[tbpg]

What is the experience for someone who doesn't have civil?

No changes. This should only change behavior for people who are using civil.

[crwilcox]

@tbpg so there is no chance of panics or anything from a missing import?

[tbpg]

@crwilcox, no. I don't think there is a way to cause a panic from a missing import in Go. If something is used, it is imported, otherwise there is a compile-time error.

[crwilcox]

Thank you for clearing things up @tbpg. I had missed that the package already depended on civil which is why I was a bit confused how this worked. lgtm.

[dnerdy]

Thank you @IlyaFaer for working on this!

I'm following up via #3089.

There's an issue loading civil dates and times on a machine when the timezone is set to anything other than UTC. Time properties are loaded in a machine's local location (see #916) and therefore need to be converted to UTC before using them to create civil values.

I think this is the adjustment that's needed:

case typeOfCivilDate:
	date := civil.DateOf(pValue.(time.Time).In(time.UTC))
	v.Set(reflect.ValueOf(date))
case typeOfCivilDateTime:
	dateTime := civil.DateTimeOf(pValue.(time.Time).In(time.UTC))
	v.Set(reflect.ValueOf(dateTime))
case typeOfCivilTime:
	timeVal := civil.TimeOf(pValue.(time.Time).In(time.UTC))
	v.Set(reflect.ValueOf(timeVal))

[codyoss]

@dnerdy Would you please open an issue for this, thanks for finding this!