DEV: adds event hook when add/remove user to group (#8038)

spec/models/group_spec.rb

@@ -806,6 +806,11 @@ describe Group do
       user.update(primary_group: group)
       expect { group.remove(user) }.to change { user.reload.primary_group }.from(group).to(nil)
     end
+
+    it 'triggers a user_removed_from_group event' do
+      events = DiscourseEvent.track_events { group.remove(user) }.map { |e| e[:event_name] }
+      expect(events).to include(:user_removed_from_group)
+    end
   end
 
   describe '#add' do
@@ -839,6 +844,25 @@ describe Group do
       expect(notification.user_id).to eq(user.id)
     end
 
+    it 'triggers a user_added_to_group event' do
+      begin
+        automatic = nil
+        called = false
+
+        DiscourseEvent.on(:user_added_to_group) do |_u, _g, options|
+          automatic = options[:automatic]
+          called = true
+        end
+
+        group.add(user)
+
+        expect(automatic).to eql(false)
+        expect(called).to eq(true)
+      ensure
+        DiscourseEvent.off(:user_added_to_group)
+      end
+    end
+
     context 'when adding a user into a public group' do
       fab!(:category) { Fabricate(:category) }