[Discuss] Expand GeoIP ingest processor support to other GeoIP database types

The [GeoIP processor](https://www.elastic.co/guide/en/elasticsearch/reference/current/geoip-processor.html) uses the GeoLite2 City, GeoLite2 Country, and GeoLite2 ASN GeoIP2 databases from [MaxMind](http://dev.maxmind.com/geoip/geoip2/geolite2/) to add information about the geographical location of an IP address during ingest pipeline processing. We have received a few requests to support other GeoIP databases such as Neustar or ipinfo.io. Given this would require implementation effort to support DB files of other formats from other sources, we'd like to hear from others if you have similar needs:

- What other GeoIP sources would you like Elasticsearch to support?
- What is the benefit of these over the currently-supported MaxMind DBs?
- Would you need additional or different fields matched from the GeoIP DB?