chore: Fix user email re-confirmation flow (#3581)

Users can change their email from profile settings. They will be logged out immediately. Users can log in again with the updated email without verifying the same. This is a security problem.

So this change enforce the user to reconfirm the email after changing it. Users can log in with the updated email only after the confirmation.

Fixes: https://huntr.dev/bounties/7afd04b4-232e-4907-8a3c-acf8bd4b5b22/

spec/models/user_spec.rb

@@ -80,4 +80,11 @@ RSpec.describe User do
       expect(token_count).to eq(1)
     end
   end
+
+  context 'when user changes the email' do
+    it 'mutates the value' do
+      user.email = 'user@example.com'
+      expect(user.will_save_change_to_email?).to be true
+    end
+  end
 end