Replace ahoy events with real data

We were tracking some events with Ahoy, but in an inconsistent way. For
example, we were tracking when a debate was created, but (probably
accidentally) we were only tracking proposals when they were created
from the management section. For budget investments and their supports,
we weren't using Ahoy events but checking their database tables instead.
And we were only using ahoy events for the charts; for the other stats,
we were using the real data.

While we could actually fix these issues and start tracking events
correctly, existing production data would remain broken because we
didn't track a certain event when it happened. And, besides, why should
we bother, for instance, to track when a debate is created, when we can
instead access that information in the debates table?

There are probably some features related to tracking an event and their
visits, but we weren't using them, and we were storing more user data
than we needed to.

So we're removing the track events, allowing us to simplify the code and
make it more consistent. We aren't removing the `ahoy_events` table in
case existing Consul Democracy installations use it, but we'll remove it
after releasing version 2.2.0 and adding a warning in the release notes.

This change fixes the proposal created chart, since we were only
tracking proposals created in the management section, and opens the
possibility to add more charts in the future using data we didn't track
with Ahoy.

Also note the "Level 2 user Graph" test wasn't testing the graph, so
we're changing it in order to test it. We're also moving it next to the
other graphs test and, since we were tracking the event when we were
confirming the phone, we're renaming to "Level 3 users".

Finally, note that, since we were tracking events when something was
created, we're including the `with_hidden` scope. This is also
consistent with the other stats shown in the admin section as well as
the public stats.

spec/system/admin/stats_spec.rb

@@ -72,18 +72,6 @@ describe "Stats", :admin do
       expect(page).to have_content "UNVERIFIED USERS\n1"
       expect(page).to have_content "TOTAL USERS\n1"
     end
-
-    scenario "Level 2 user Graph" do
-      create(:geozone)
-      visit account_path
-      click_link "Verify my account"
-      verify_residence
-      confirm_phone
-
-      visit admin_stats_path
-
-      expect(page).to have_content "LEVEL TWO USERS\n1"
-    end
   end
 
   describe "Budget investments" do
@@ -150,15 +138,9 @@ describe "Stats", :admin do
     end
   end
 
-  context "graphs" do
-    scenario "event graphs", :with_frozen_time do
-      visit new_debate_path
-      fill_in_new_debate_title with: "A title for a debate"
-      fill_in_ckeditor "Initial debate text", with: "This is very important because..."
-      check "debate_terms_of_service"
-      click_button "Start a debate"
-
-      expect(page).to have_content "Debate created successfully."
+  describe "graphs", :with_frozen_time do
+    scenario "event graphs" do
+      create(:debate)
 
       visit admin_stats_path
 
@@ -172,6 +154,19 @@ describe "Stats", :admin do
         expect(page).to have_content Date.current.strftime("%Y-%m-%d")
       end
     end
+
+    scenario "Level 3 user Graph" do
+      create(:user, :level_three)
+
+      visit admin_stats_path
+      click_link "level_3_user"
+
+      expect(page).to have_content "Level 3 User (1)"
+
+      within("#graph") do
+        expect(page).to have_content Date.current.strftime("%Y-%m-%d")
+      end
+    end
   end
 
   context "Proposal notifications" do