Fix regression with logic to add user primary email to emails

A recent fix for the case when skip_reconfirmation! is called
unfortunately introduced a regression for users that are created as
unconfirmed and confirmed later. This commit fixes it, and introduces
tests for this case and other ones.

Changelog: fixed

app/models/user.rb

@@ -282,7 +282,7 @@ class User < ApplicationRecord
   after_update :username_changed_hook, if: :saved_change_to_username?
   after_destroy :post_destroy_hook
   after_destroy :remove_key_cache
-  after_save if: -> { saved_change_to_email? && confirmed? } do
+  after_save if: -> { (saved_change_to_email? || saved_change_to_confirmed_at?) && confirmed? } do
     email_to_confirm = self.emails.find_by(email: self.email)
 
     if email_to_confirm.present?

spec/models/user_spec.rb

@@ -1560,7 +1560,7 @@ RSpec.describe User do
       end
 
       it 'adds the confirmed primary email to emails' do
-        expect(user.emails.confirmed.map(&:email)).not_to include(user.email)
+        expect(user.emails.confirmed.map(&:email)).not_to include(user.unconfirmed_email)
 
         user.confirm
 
@@ -1619,14 +1619,23 @@ RSpec.describe User do
     context 'when the email is changed but not confirmed' do
       let(:user) { create(:user, email: 'primary@example.com') }
 
-      it 'does not add the new email to emails yet' do
+      before do
         user.update!(email: 'new_primary@example.com')
+      end
 
+      it 'does not add the new email to emails yet' do
         expect(user.unconfirmed_email).to eq('new_primary@example.com')
         expect(user.email).to eq('primary@example.com')
         expect(user).to be_confirmed
         expect(user.emails.pluck(:email)).not_to include('new_primary@example.com')
       end
+
+      it 'adds the new email to emails upon confirmation' do
+        user.confirm
+        expect(user.email).to eq('new_primary@example.com')
+        expect(user).to be_confirmed
+        expect(user.emails.pluck(:email)).to include('new_primary@example.com')
+      end
     end
 
     context 'when the user is created as not confirmed' do
@@ -1636,6 +1645,11 @@ RSpec.describe User do
         expect(user).not_to be_confirmed
         expect(user.emails.pluck(:email)).not_to include('primary@example.com')
       end
+
+      it 'adds the email to emails upon confirmation' do
+        user.confirm
+        expect(user.emails.pluck(:email)).to include('primary@example.com')
+      end
     end
 
     context 'when the user is created as confirmed' do