metrics: add counter for created/destroyed users

.rubocop.yml

@@ -134,3 +134,6 @@ Style/EndlessMethod:
 
 Style/TrailingCommaInHashLiteral:
   EnforcedStyleForMultiline: consistent_comma
+
+Style/TrailingCommaInArguments:
+  EnforcedStyleForMultiline: consistent_comma

app/models/user.rb

@@ -85,8 +85,14 @@ class User < ApplicationRecord # rubocop:disable Metrics/ClassLength
     end
   end
 
+  after_destroy do
+    Retrospring::Metrics::USERS_DESTROYED.increment
+  end
+
   after_create do
     Profile.create(user_id: id) if Profile.where(user_id: id).count.zero?
+
+    Retrospring::Metrics::USERS_CREATED.increment
   end
 
   # use the screen name as parameter for url helpers

lib/retrospring/metrics.rb

@@ -43,6 +43,16 @@ module Retrospring
       docstring: "How many comments got created"
     )
 
+    USERS_CREATED = counter(
+      :retrospring_users_created_total,
+      docstring: "How many users got created"
+    )
+
+    USERS_DESTROYED = counter(
+      :retrospring_users_destroyed_total,
+      docstring: "How many users deleted their accounts"
+    )
+
     # metrics from Sidekiq::Stats.new
     SIDEKIQ = {
       processed:      gauge(

spec/models/user_spec.rb

@@ -33,6 +33,45 @@ RSpec.describe User, type: :model do
     end
   end
 
+  describe "callbacks" do
+    describe "before_destroy" do
+      it "marks reports about this user as deleted" do
+        other_user = FactoryBot.create(:user)
+        other_user.report me, "va tutto benissimo"
+
+        expect { me.destroy }
+          .to change { Reports::User.find_by(target_id: me.id).deleted? }
+          .from(false)
+          .to(true)
+      end
+    end
+
+    describe "after_destroy" do
+      it "increments the users_destroyed metric" do
+        expect { me.destroy }.to change { Retrospring::Metrics::USERS_DESTROYED.values.values.sum }.by(1)
+      end
+    end
+
+    describe "after_create" do
+      subject :user do
+        User.create!(
+          screen_name: "konqi",
+          email:       "konqi@example.rrerr.net",
+          password:    "dragonsRQt5",
+        )
+      end
+
+      it "creates a profile for the user" do
+        expect { user }.to change { Profile.count }.by(1)
+        expect(Profile.find_by(user:).user).to eq(user)
+      end
+
+      it "increments the users_created metric" do
+        expect { user }.to change { Retrospring::Metrics::USERS_CREATED.values.values.sum }.by(1)
+      end
+    end
+  end
+
   describe "custom sharing url validation" do
     subject do
       FactoryBot.build(:user, sharing_custom_url: url).tap(&:validate).errors[:sharing_custom_url]