Add /user_actions page.

Add a /user_actions page. This page shows you a global timeline of
(almost) all activity on the site, including uploads, comments, votes,
edits, forum posts, and so on.

The main things it doesn't include are post edits, pool edits, and
favorites (posts and pools live in a separate database, and favorites
don't have the timestamps we need for ordering).

This page is useful for moderation purposes because it lets you see a
history of almost all of a user's activity on a single page.

Currently this page is mod-only. In the future it will be open to all
users, so you can view the history of your own site activity, or the
activity of others.

test/factories/moderation_report.rb

@@ -3,5 +3,6 @@ FactoryBot.define do
     creator
     reason {"xxx"}
     status { :pending }
+    model { build(:comment) }
   end
 end

test/factories/user_event.rb

@@ -2,5 +2,6 @@ FactoryBot.define do
   factory(:user_event) do
     user
     user_session
+    category { :login }
   end
 end

test/functional/user_actions_controller_test.rb

@@ -0,0 +1,72 @@
+require 'test_helper'
+
+class UserActionsControllerTest < ActionDispatch::IntegrationTest
+  context "The user actions controller" do
+    context "index action" do
+      setup do
+        @user = create(:user)
+
+        as(@user) do
+          create(:artist)
+          create(:artist_commentary)
+          create(:ban)
+          create(:bulk_update_request)
+          create(:comment)
+          create(:comment_vote)
+          create(:dmail)
+          create(:favorite_group)
+          create(:forum_post)
+          create(:forum_post_vote)
+          create(:forum_topic)
+          create(:mod_action)
+          create(:moderation_report)
+          create(:note)
+          create(:post)
+          create(:post_appeal)
+          create(:post_approval)
+          create(:post_disapproval)
+          create(:post_flag)
+          create(:post_replacement)
+          create(:post_vote)
+          create(:wiki_page)
+          create(:saved_search)
+          create(:tag)
+          create(:tag_alias)
+          create(:tag_implication)
+          create(:upload)
+          create(:user_event)
+          create(:user_feedback)
+          create(:user_name_change_request)
+          create(:user_upgrade)
+          create(:wiki_page)
+        end
+      end
+
+      should "render for the owner" do
+        get_auth user_events_path(limit: 1000), create(:admin_user)
+        assert_response :success
+      end
+
+      should "render for an admin" do
+        get_auth user_events_path(limit: 1000), create(:admin_user)
+        assert_response :success
+      end
+
+      should "render for a mod" do
+        get_auth user_events_path(limit: 1000), create(:moderator_user)
+        assert_response :success
+      end
+
+      should "fail for a normal user" do
+        get_auth user_actions_path(limit: 1000), create(:user)
+        assert_response 403
+      end
+
+      should "render when filtering on a single user" do
+        get_auth user_events_path(user_id: @user.id, limit: 1000), create(:owner_user)
+        assert_response :success
+      end
+    end
+  end
+end
+