Fix the `chrono` RUSTSEC advisory

[hug-dev]

Hello!

I was receiving a lot of mail from our cargo audit nightly checks and finally decided to investigate :). It appears that the error is coming from the chrono crate and the RUSTSEC-2020-0159 advisory.

I have seen a few PR where people replace chrono with time (including some of the dependencies). See here for example. I suggest that the same is done here too!

[ionut-arm]

This was in my todo list for some time, need to finish some other stuff first and then I'll try to get a fix for this.

[ionut-arm]

I have an update here: I've started working on a fix for this issue, however it's gone beyond what I expected.

Apart from the direct dependency on chrono, a few of the other dependencies depend themselves on chrono, and that's been a pain to avoid. I replaced x509-parser and simple_asn1 with the picky-... alternatives, but couldn't find a solution for the jsonwebtoken-jsonwebkey pair of crates. jsonwebtoken is currently in a 8.0.0-alpha version which is expected to be the last before the stable release, and this release would include a fix for the chrono issue, however jsonwebkey will also need to be updated accordingly.

I'll try to get a fix in for x509-parser (instead of replacing it) and to also migrate jsonwebkey to the new version of jsonwebtoken when that's possible.

I'll give more updates as they happen.

[maxlambrecht]

I got some time to take a stab at this issue.

I replaced chrono dependency by the time crate and updated deps simple_asn1, x509_parser and zeroize to versions that no longer depend on chrono. See #21

What is missing is updating jsonwebtoken to 0.8, this version removed the chrono crate. I'm waiting to do that until this PR on the jsonwebkey crate is merged. Also I created an issue on that repo: update jsonwebtoken

[maxlambrecht]

Version v0.2.1 was published 🎉

[hug-dev]

Nice!! Thanks 👍