Add optional feature to accept RFC 3339 timestamps, for compatibility with Auth0

[andrewhickman]

Fixes #23

[codecov]

Codecov Report

Merging #55 (ffaf7d3) into main (f4a9902) will decrease coverage by 0.03%.
The diff coverage is 69.69%.

@@            Coverage Diff             @@
##             main      #55      +/-   ##
==========================================
- Coverage   76.81%   76.78%   -0.04%     
==========================================
  Files          16       16              
  Lines        3472     3480       +8     
==========================================
+ Hits         2667     2672       +5     
- Misses        805      808       +3     

Impacted Files	Coverage Δ
src/claims.rs	13.58% <ø> (ø)
src/types.rs	73.00% <60.00%> (-0.83%)	⬇️
src/id_token.rs	93.87% <100.00%> (+0.03%)	⬆️
src/macros.rs	73.13% <100.00%> (+1.07%)	⬆️
src/verification.rs	84.55% <100.00%> (ø)

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[ramosbugs]

Thank you!

[ThomasLamprecht]

Is there any reason that this is an (optional) feature? It doesn't pull in any new dependency FWICT and runtime overhead of that additional match shouldn't be too bad, and users of this crate would benefit from working with more providers by default.

I mean, I'll enable it and be done for my use case, so no biggie for me personally, but after reading the release notes and upgrading did not solve auth0 access I had to read more closely and check the PR itself, I wondered for the reason behind that feature guard.

[ramosbugs]

it's optional because Auth0 does not follow the OpenID Connect standard, and this library adheres to the standard in its default configuration