Add new geolocatio-country-code redirect condition type

[acelaya]

Part of #1774

Add a new type of condition for the dynamic rule-based redirection system.

This condition checks if the ISO 3166-1 alpha-2 country code resulting of geolocating current visitor matches configured country code.

This condition will never match if geolocation is not configured, or it is disabled, and there's always a chance of a visitor to be incorrectly geolocated, so there's a small chance of false negatives/positives.

During condition creation, only the country code will be validated, but Shlink won't warn you if geolocation is not configured/enabled at that point.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 93.68%. Comparing base (9a69d06) to head (7ddb3e7).
Report is 9 commits behind head on develop.

Additional details and impacted files

@@              Coverage Diff              @@
##             develop    #2257      +/-   ##
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+ Coverage      93.64%   93.68%   +0.04%     
- Complexity      1637     1647      +10     
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  Files            271      272       +1     
  Lines           5726     5768      +42     
=============================================
+ Hits            5362     5404      +42     
  Misses           364      364              

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