Check if a datetime is in millis

[mbroshi-stripe]

Why?

A bug was reported in #3253 where the Stripe API is returning a datetime in milliseconds instead of seconds. That's causing a ArgumentOutOfRangeException when trying to deserialize the last_seen_at field. This PR addresses that issue by detecting if a returned value is in millis or seconds before trying to deserialize it to a DateTime.

What?

• Updates UnixDateTimeConverter and STJUnixDateTimeConverter to convert large values as milliseconds and smaller values as seconds.

See Also

Changelog

• Bug fix for #3253. UnixDateTimeConverter now handles timestamps in milliseconds.

[kerams]

Why not convert all those DateTime into DateTimeOffset at long last, especially if you're releasing a major version.

[mbroshi-stripe]

Why not convert all those DateTime into DateTimeOffset at long last, especially if you're releasing a major version.

@kerams Thanks for the idea! Can you open an issue with that? That seems like a much bigger change, but we can consider it separately.