added firstMatch support

[komorran]

Hi, I've made some changes due to this issue - https://github.com/aerokube/ggr/issues/314 Changed data structure for capabilities in proxy.go, updated logic for firstMatch support and updated/implemented tests. Please let me know what I maybe should change or fix.

[codecov[bot]]

Codecov Report

Merging #352 (e23ebe7) into master (ad43f36) will increase coverage by 0.42%. The diff coverage is 98.41%.

@@            Coverage Diff             @@
##           master     #352      +/-   ##
==========================================
+ Coverage   89.72%   90.15%   +0.42%     
==========================================
  Files           4        4              
  Lines         584      589       +5     
==========================================
+ Hits          524      531       +7     
+ Misses         47       46       -1     
+ Partials       13       12       -1     

Flag	Coverage Δ
go	90.15% <98.41%> (+0.42%)	:arrow_up:

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
proxy.go	94.61% <98.41%> (+0.47%)	:arrow_up:

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[vania-pooh]

@komorran sorry for the delay. We'll look into it as soon as possible.

[vania-pooh]

Fixed in #353. Thank you for contribution!