FIX: makes invitees search case insensitive

FIX: makes invitees search case insensitive

diff --git a/app/controllers/discourse_calendar/invitees_controller.rb b/app/controllers/discourse_calendar/invitees_controller.rb
index 01d7f80..5b10f63 100644
--- a/app/controllers/discourse_calendar/invitees_controller.rb
+++ b/app/controllers/discourse_calendar/invitees_controller.rb
@@ -15,7 +15,9 @@ module DiscourseCalendar
       post_event_invitees = PostEvent.find(params['post-event-id']).invitees
 
       if params[:filter]
-        post_event_invitees = post_event_invitees.joins(:user).where("users.username LIKE '%#{params[:filter]}%'")
+        post_event_invitees = post_event_invitees
+          .joins(:user)
+          .where("LOWER(users.username) LIKE :filter", filter: "%#{params[:filter].downcase}%")
       end
 
       render json: ActiveModel::ArraySerializer.new(post_event_invitees.limit(10), each_serializer: InviteeSerializer).as_json

GitHub sha: 45e19cbb