Make sure SimpleDateFormat is set to UTC timezone

[gferon]

• All new/changed/fixed functionality is covered by tests (or N/A)
• I have added documentation for all new/changed functionality (or N/A)

📋 Changes

After spending quite some time trying to understand why our access tokens would not be refreshed, I realized that something was wrong with the expiresAt field. The issue affects (at least) Android because the UTC timezone is added in the format while the formatter itself is timezone-unaware.

With the following added print statements, you can observe that the Credentials.expiresAt is formatted from local time with an appended Z, which means we lose the timezone information.

I/System.out(18918): RenewApiRequestHandler::onSuccess credentials.expiresAt Tue Jul 23 08:49:05 GMT+02:00 2024
I/System.out(18918): RenewApiRequestHandler::onSuccess formattedDate 2024-07-23T08:49:05.555Z

Making sure all SimpleDateFormat are set to the UTC timezone fixes the issue, but since java.util.Date is notably confusing to work with, a better fix would maybe be to use java.time.Instant (see alternative PR #469) and either call .toInstant().toString() everywhere (and Instant.parse()) which always work with ISO-8601 representation.

📎 References

🎯 Testing

Print the expiresAt date in Flutter with and without this patch. This unit tests didn't catch this problem because the test had the same implementation issue.

[desusai7]

Hi @gferon,

We appreciate your time on raising this PR, however I am closing it as we are considering the PR #469 raised by you !

Thanks