FEATURE: Redeem invites for existent users (#15866)

This adds logic to increase an `InvitedUser` record, increase
`redemption_count` and create a `:invitee_accepted` to let the inviter
know that the invitee used the invite.

Initial support for this was implemented in commit 9969631.

app/controllers/invites_controller.rb

@@ -22,31 +22,36 @@ class InvitesController < ApplicationController
     invite = Invite.find_by(invite_key: params[:id])
     if invite.present? && invite.redeemable?
       if current_user
-        added_to_group = false
+        InvitedUser.transaction do
+          invited_user = InvitedUser.find_or_initialize_by(user: current_user, invite: invite)
+          if invited_user.new_record?
+            invited_user.save!
+            Invite.increment_counter(:redemption_count, invite.id)
+            invite.invited_by.notifications.create!(
+              notification_type: Notification.types[:invitee_accepted],
+              data: { display_username: current_user.username }.to_json
+            )
+          end
+        end
 
         if invite.groups.present?
           invite_by_guardian = Guardian.new(invite.invited_by)
           new_group_ids = invite.groups.pluck(:id) - current_user.group_users.pluck(:group_id)
           new_group_ids.each do |id|
             if group = Group.find_by(id: id)
-              if invite_by_guardian.can_edit_group?(group)
-                group.add(current_user)
-                added_to_group = true
-              end
+              group.add(current_user) if invite_by_guardian.can_edit_group?(group)
             end
           end
         end
 
-        create_topic_invite_notifications(invite, current_user)
-
         if topic = invite.topics.first
-          new_guardian = Guardian.new(current_user)
-          return redirect_to(topic.url) if new_guardian.can_see?(topic)
-        elsif added_to_group
-          return redirect_to(path("/"))
+          if current_user.guardian.can_see?(topic)
+            create_topic_invite_notifications(invite, current_user)
+            return redirect_to(topic.url)
+          end
         end
 
-        return ensure_not_logged_in
+        return redirect_to(path("/"))
       end
 
       email = Email.obfuscate(invite.email)

spec/requests/invites_controller_spec.rb

@@ -105,13 +105,16 @@ describe InvitesController do
       expect(Notification.where(notification_type: Notification.types[:invited_to_topic], topic: topic).count).to eq(1)
     end
 
-    it 'fails for logged in users' do
-      sign_in(Fabricate(:user))
+    it 'creates a notification to inviter' do
+      topic = Fabricate(:topic)
+      TopicInvite.create!(topic: topic, invite: invite)
+
+      sign_in(user)
 
       get "/invites/#{invite.invite_key}"
-      expect(response.status).to eq(200)
-      expect(response.body).to_not have_tag(:script, with: { src: '/assets/application.js' })
-      expect(response.body).to include(I18n.t('login.already_logged_in'))
+      expect(response).to redirect_to(topic.url)
+      expect(Notification.where(user: user, notification_type: Notification.types[:invited_to_topic], topic: topic).count).to eq(1)
+      expect(Notification.where(user: invite.invited_by, notification_type: Notification.types[:invitee_accepted]).count).to eq(1)
     end
 
     it 'fails if invite does not exist' do