Add tournament serializers

SimpleTournamentSerializer excludes relationships and should be used for
listings

app/serializers/simple_tournament_serializer.rb

@@ -0,0 +1,5 @@
+# frozen_string_literal: true
+
+class SimpleTournamentSerializer < ApplicationSerializer
+  attributes :name, :code, :description, :public
+end

app/serializers/tournament_serializer.rb

@@ -0,0 +1,6 @@
+# frozen_string_literal: true
+
+class TournamentSerializer < SimpleTournamentSerializer
+  has_many :teams
+  has_many :stages
+end