FEATURE: Add 'groups' option to polls (#8469)

This options can be used to restrict polls to certain groups.

plugins/poll/app/models/poll.rb

@@ -78,6 +78,7 @@ end
 #  created_at       :datetime         not null
 #  updated_at       :datetime         not null
 #  chart_type       :integer          default("bar"), not null
+#  groups           :string
 #
 # Indexes
 #

plugins/poll/app/serializers/poll_serializer.rb

@@ -13,7 +13,8 @@ class PollSerializer < ApplicationSerializer
              :voters,
              :close,
              :preloaded_voters,
-             :chart_type
+             :chart_type,
+             :groups
 
   def public
     true
@@ -35,6 +36,10 @@ class PollSerializer < ApplicationSerializer
     object.step.present? && object.number?
   end
 
+  def include_groups?
+    groups.present?
+  end
+
   def options
     object.poll_options.map { |o| PollOptionSerializer.new(o, root: false).as_json }
   end