log adding the user to a group

app/services/discourse_donations/rewards.rb

@@ -2,6 +2,8 @@
 
 module DiscourseDonations
   class Rewards
+    attr_reader :user
+
     def initialize(user)
       @user = user
     end
@@ -9,13 +11,19 @@ module DiscourseDonations
     def add_to_group(name)
       grp = ::Group.find_by_name(name)
       return if grp.nil?
-      grp.add(@user)
+      log_group_add(grp)
+      grp.add(user)
     end
 
     def grant_badge(name)
       badge = ::Badge.find_by_name(name)
       return if badge.nil?
-      BadgeGranter.grant(badge, @user)
+      BadgeGranter.grant(badge, user)
+    end
+
+    def log_group_add(grp)
+      system_user = User.find(-1)
+      GroupActionLogger.new(system_user, grp).log_add_user_to_group(user)
     end
   end
 end

spec/services/discourse_donations/rewards_spec.rb

@@ -9,15 +9,22 @@ module DiscourseDonations
     it 'adds the user to a group' do
       Group.expects(:find_by_name).with(grp.name).returns(grp)
       grp.expects(:add).with(user)
+      subject.expects(:log_group_add).once
       subject.add_to_group(grp.name)
     end
 
     it 'does not add the user to a group' do
       Group.expects(:find_by_name).with(grp.name).returns(nil)
       grp.expects(:add).never
+      subject.expects(:log_group_add).never
       expect(subject.add_to_group(grp.name)).to be_falsy
     end
 
+    it 'logs the group add' do
+      GroupActionLogger.any_instance.expects(:log_add_user_to_group)
+      subject.add_to_group(grp.name)
+    end
+
     it 'grants the user a badge' do
       badge = Fabricate(:badge)
       BadgeGranter.expects(:grant).with(badge, user)