users: track logins, signups, and other user events.

Add tracking of certain important user actions. These events include:

* Logins
* Logouts
* Failed login attempts
* Account creations
* Account deletions
* Password reset requests
* Password changes
* Email address changes

This is similar to the mod actions log, except for account activity
related to a single user.

The information tracked includes the user, the event type (login,
logout, etc), the timestamp, the user's IP address, IP geolocation
information, the user's browser user agent, and the user's session ID
from their session cookie. This information is visible to mods only.

This is done with three models. The UserEvent model tracks the event
type (login, logout, password change, etc) and the user. The UserEvent
is tied to a UserSession, which contains the user's IP address and
browser metadata. Finally, the IpGeolocation model contains the
geolocation information for IPs, including the city, country, ISP, and
whether the IP is a proxy.

This tracking will be used for a few purposes:

* Letting users view their account history, to detect things like logins
  from unrecognized IPs, failed logins attempts, password changes, etc.
* Rate limiting failed login attempts.
* Detecting sockpuppet accounts using their login history.
* Detecting unauthorized account sharing.

test/unit/ip_geolocation_test.rb

@@ -0,0 +1,72 @@
+require 'test_helper'
+
+class IpGeolocationTest < ActiveSupport::TestCase
+  context "IpGeolocation: " do
+    context "the create_or_update! method" do
+      should "create a new record if the IP record doesn't already exist" do
+        assert_difference("IpGeolocation.count", 1) do
+          IpGeolocation.create_or_update!("1.1.1.1")
+        end
+      end
+
+      should "update an existing record if the IP record already exists" do
+        @ip1 = IpGeolocation.create_or_update!("1.1.1.1")
+        @ip1.update(asn: -1)
+        @ip2 = IpGeolocation.create_or_update!("1.1.1.1")
+
+        assert_equal(1, IpGeolocation.count)
+        assert_equal(@ip1.id, @ip2.id)
+        assert_equal(13335, @ip1.reload.asn)
+      end
+
+      should "return nothing for an invalid IP" do
+        assert_nil(IpGeolocation.create_or_update!("0.0.0.0"))
+      end
+
+      should "return nothing for a local IP" do
+        assert_nil(IpGeolocation.create_or_update!("127.0.0.1"))
+        assert_nil(IpGeolocation.create_or_update!("10.0.0.1"))
+        assert_nil(IpGeolocation.create_or_update!("fe80::1"))
+        assert_nil(IpGeolocation.create_or_update!("::1"))
+      end
+
+      should "work for a residential IP" do
+        @ip = IpGeolocation.create_or_update!("2a01:0e35:2f22:e3d0::1")
+
+        assert_equal(28, @ip.network.prefix)
+        assert_equal(false, @ip.is_proxy?)
+        assert_equal(48.75919, @ip.latitude)
+        assert_equal(2.16969, @ip.longitude)
+        assert_equal("Free SAS", @ip.organization)
+        assert_equal("Europe/Paris", @ip.time_zone)
+        assert_equal("EU", @ip.continent)
+        assert_equal("FR", @ip.country)
+        assert_equal("FR-IDF", @ip.region)
+        assert_equal("Jouy-en-Josas", @ip.city)
+        assert_nil(@ip.carrier)
+      end
+
+      should "work for a mobile IP" do
+        @ip = IpGeolocation.create_or_update!("37.173.153.166")
+        assert_equal("Free Mobile", @ip.carrier)
+      end
+
+      should "work for a proxy IP" do
+        @ip = IpGeolocation.create_or_update!("31.214.184.59")
+        assert_equal("Soluciones Corporativas IP SL", @ip.organization)
+        assert_equal(true, @ip.is_proxy?)
+      end
+
+      should "work for a cloud hosting IP" do
+        @ip = IpGeolocation.create_or_update!("157.230.244.215")
+        assert_equal("DigitalOcean LLC", @ip.organization)
+        assert_equal(true, @ip.is_proxy?)
+      end
+
+      should "work for a bogon IP" do
+        @ip = IpGeolocation.create_or_update!("103.10.192.0")
+        assert_equal(true, @ip.is_proxy?)
+      end
+    end
+  end
+end