Friendly urls for tracks

Don't use tracks ids in urls
Add short_name to tracks and use that in urls as the identifier

db/migrate/20170629162450_add_short_name_to_tracks.rb

@@ -0,0 +1,39 @@
+class AddShortNameToTracks < ActiveRecord::Migration
+  class TmpProgram < ActiveRecord::Base
+    self.table_name = 'programs'
+  end
+
+  class TmpTrack < ActiveRecord::Base
+    self.table_name = 'tracks'
+  end
+
+  def change
+    add_column :tracks, :short_name, :string
+
+    TmpTrack.reset_column_information
+
+    TmpProgram.find_each do |program|
+      # Keeps count of how many times we've encountered a short_name
+      track_name_counter = {}
+
+      TmpTrack.where(program_id: program.id).find_each do |track|
+        # Replace spaces with undercores and remove the non alphanumeric characters that aren't underscores or dashes
+        short_name = track.name.tr(' ', '_').tr('^a-zA-Z0-9_-', '')
+
+        # If we've seen that short_name before then add the counter in the end to avoid collisions
+        if track_name_counter[short_name]
+          track_name_counter[short_name] += 1
+          short_name += "_#{track_name_counter[short_name]}"
+        else
+          # Initialize the counter
+          track_name_counter[short_name] = 0 unless track_name_counter[short_name]
+        end
+
+        track.short_name = short_name
+        track.save!
+      end
+    end
+
+    change_column_null :tracks, :short_name, false
+  end
+end