Add relevance field for track requests

The requester can now provide more info about the track and himself

spec/models/track_spec.rb

@@ -48,6 +48,22 @@ describe Track do
       it { is_expected.to_not validate_presence_of(:room) }
     end
 
+    context 'when self_organized? returns true' do
+      before :each do
+        allow(subject).to receive(:self_organized?).and_return(true)
+      end
+
+      it { is_expected.to validate_presence_of(:relevance) }
+    end
+
+    context 'when self_organized? returns false' do
+      before :each do
+        allow(subject).to receive(:self_organized?).and_return(false)
+      end
+
+      it { is_expected.to_not validate_presence_of(:relevance) }
+    end
+
     describe '#valid_dates' do
       before :each do
         @conference = create(:conference, start_date: 1.day.ago, end_date: 2.days.from_now)