Add MaxMind GeoIP2 Anonymous IP support

[adiov]

What this PR does / why we need it:

The NGINX Ingress Controller already has extensive support for many MaxMind's GeoIP2 databases. It is, however, missing support for another crucial MaxMind GeoIP2 database, the GeoIP2 Anonymous IP database. This PR adds support for it in a way that conforms to the way other MaxMind databases are supported.

For those with licence to the GeoIP2 Anonymous IP database, an additional entry to --maxmind-edition-ids can be supplied as such:

--maxmind-edition-ids="GeoLite2-City,GeoLite2-ASN,GeoIP2-Anonymous-IP"

This will trigger the existing database download and checking flow. If the database is downloaded successfully or is made available with a mounted volume, this PR exposes 3 new variables: $geoip2_is_anon, $geoip2_is_hosting_provider, and $geoip2_is_public_proxy. Those variables can then be freely used in a ConfigMap to add further functionality, such as annotating logs or blocking requests altogether.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Which issue/s this PR fixes

How Has This Been Tested?

With the new template loaded, new proxy_set_header lines to the deployment's config.yaml were added as such:

proxy_set_header X-Is-Anon $geoip2_is_anon;
proxy_set_header X-Is-Hosting-Provider $geoip2_is_hosting_provider;
proxy_set_header X-Is-Public-Proxy $geoip2_is_public_proxy;

After deployment, requests from AWS EC2 and Tor were sent to one of the Ingress endpoints. The forwarded requests were observed to have the correct header values indicating that the requests were "anonymous" or came from a hosting provider.

Checklist:

• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I've read the CONTRIBUTION guide
• I have added tests to cover my changes.
• All new and existing tests passed.

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[k8s-ci-robot]

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[adiov]

/assign @bowei

[aledbf]

/ok-to-test

[aledbf]

@adiov please don't assign PRs manually

[adiov]

/retest

[aledbf]

/lgtm
/approve

[aledbf]

@adiov thanks!

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: adiov, aledbf

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