Maxmind: Use registered_country instead of country

[th-certbund]

MaxMind provides different country attributes for an IP:

• country: Country where MaxMind believes the user is located.
• registered_country: Country registered with the network range.

Incidents are usually reported to the network owner responsible for the affected IP or the respective national CSIRT. So in particular for CDN networks or satellite providers, we are not interested in the country a user is (potentially) located but in the location of the network owner.

Example for DE vs. US:

network:IP-Network:38.87.230.0/23
network:Org-Name:Interlax Telecom
network:Street-Address:50 NE 9th St.
network:City:Miami
network:State:FL
network:Country:US

Maxmind results:

country: DE
registered_country: US

Example for DE vs. AF:

inetnum:        180.222.136.0 - 180.222.143.0
netname:        Etisalat
descr:          Etisalat Afghanistan
country:        AF

Maxmind results:

country: DE
registered_country: AF

[codecov-io]

Codecov Report

Merging #1344 into develop will not change coverage.
The diff coverage is 0%.

@@           Coverage Diff            @@
##           develop    #1344   +/-   ##
========================================
  Coverage    74.63%   74.63%           
========================================
  Files          295      295           
  Lines        13518    13518           
  Branches      1831     1831           
========================================
  Hits         10089    10089           
  Misses        3015     3015           
  Partials       414      414

Impacted Files	Coverage Δ
intelmq/bots/experts/maxmind_geoip/expert.py	25.64% <0%> (ø)	⬆️

[ghost]

cc @aaronkaplan

[ghost]

I extended it a bit by introducing a parameter use_registered to ensure backwards-compatibility and the possibility to chose. And at the chance I also fixed the docs.
26a64e0