Add certificate expiration support

[Exagone313]

Fixes #28

[codecov-io]

Codecov Report

Merging #37 (27c8c55) into master (f273ee4) will increase coverage by 0.14%.
The diff coverage is 85.71%.

@@            Coverage Diff             @@
##           master      #37      +/-   ##
==========================================
+ Coverage   84.67%   84.82%   +0.14%     
==========================================
  Files          14       14              
  Lines         509      514       +5     
==========================================
+ Hits          431      436       +5     
  Misses         56       56              
  Partials       22       22              

Impacted Files	Coverage Δ
core/condition.go	87.62% <75.00%> (+0.26%)	⬆️
core/service.go	68.29% <100.00%> (+1.20%)	⬆️

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[TwiN]

Great work and thank you for the contribution @Exagone313!

I'll merge this into master, run a few tests on my end this feature will be included in the next release.

[Exagone313]

The pleasure is mine, it's been a while I needed a tool like yours, I just missed this feature.

[TwiN]

@Exagone313 I was just about to release it in v1.6.0, but the more I think about it, the more I think it'd be silly to leave it in milliseconds.

Does anybody realistically care about millisecond precision for certificate expiration?

I'm thinking that it may be better to just have it in days instead (e.g. [CERTIFICATE_EXPIRATION] > 7 where 7 is the number of days)

What do you think @Exagone313 @r3vit?

[Exagone313]

@TwinProduction I think it makes more sense to keep all durations in the same "unit" and rather replace strings such as 7d.

[TwiN]

Released in v1.6.0