Timezone handling in W3C Standard VC Credentials and Proofs

[swcurran]

Two issues have come up with time handling in ACA-Py around timestamps related to W3C Standard VCs and VPs:

1. By default, the python ISO date formatter does not include the timezone and we should include the timezone. Please update places where we are writing date to include a timezone in all cases.
2. The ISO860 format, as required in the W3C VC Spec., does not require a timezone. As such, in reading dates, make sure dates with and without a timezone can be handled. Where timezone is not included, I think the right thing is to assume UTC. Happy to have that confirmed on rocketchat.

Thanks