Add new IP address search page.

Add a new IP address search page at /ip_addresses. Replaces the old
search page at /moderator/ip_addrs.

On user profile pages, show the user's last known IP to mods. Also add
search links for finding other IPs or accounts associated with the user.

IP address search uses a big UNION ALL statement to merge IP addresses
across various tables into a single view. This makes searching easier,
but is known to timeout in certain cases.

Fixes #4207 (the new IP search page supports searching by subnet).

test/functional/ip_addresses_controller_test.rb

@@ -0,0 +1,39 @@
+require 'test_helper'
+
+class IpAddressesControllerTest < ActionDispatch::IntegrationTest
+  context "The IP addresses controller" do
+    setup do
+      @mod = create(:mod_user, last_ip_addr: "1.2.3.4")
+      @user = create(:user, last_ip_addr: "5.6.7.8")
+
+      CurrentUser.scoped(@user, "5.6.7.9") do
+        @note = create(:note)
+        @artist = create(:artist)
+      end
+    end
+
+    context "index action" do
+      should "list all IP addresses" do
+        get_auth ip_addresses_path, @mod
+        assert_response :success
+      end
+
+      should "allow searching by subnet" do
+        get_auth ip_addresses_path(search: { ip_addr: "5.0.0.0/8" }), @mod, as: :json
+
+        assert_response :success
+        assert(response.parsed_body.present?)
+      end
+
+      should "allow grouping by user" do
+        get_auth ip_addresses_path(search: { ip_addr: @user.last_ip_addr, group_by: "user" }), @mod
+        assert_response :success
+      end
+
+      should "allow grouping by IP" do
+        get_auth ip_addresses_path(search: { user_id: @user.id, group_by: "ip_addr" }), @mod
+        assert_response :success
+      end
+    end
+  end
+end