Add more info to the competition API

WcaOnRails/Gemfile

@@ -102,6 +102,7 @@ gem 'sprockets-rails'
 gem 'fuzzy-string-match'
 gem 'sidekiq'
 gem 'sidekiq-cron'
+gem 'deep_merge', require: 'deep_merge/rails_compat'
 
 group :development, :test do
   gem 'spring'

WcaOnRails/Gemfile.lock

@@ -238,6 +238,7 @@ GEM
     date (3.3.3)
     debug_inspector (1.0.0)
     declarative (0.0.20)
+    deep_merge (1.2.2)
     devise (4.9.2)
       bcrypt (~> 3.0)
       orm_adapter (~> 0.1)
@@ -775,6 +776,7 @@ DEPENDENCIES
   daemons
   database_cleaner
   datetimepicker-rails!
+  deep_merge
   devise
   devise-bootstrap-views
   devise-i18n

WcaOnRails/app/controllers/api/v0/competitions_controller.rb

@@ -17,9 +17,20 @@ def index
     paginate json: competitions
   end
 
+  COMPETITION_INFO_SERIALIZE_OPTIONS = {
+    only: %w[extra_registration_requirements enable_donations refund_policy_limit_date event_change_deadline_date waiting_list_deadline_date on_the_spot_registration on_the_spot_entry_fee_lowest_denomination qualification_results
+             event_restrictions base_entry_fee_lowest_denomination currency_code allow_registration_edits allow_registration_self_delete_after_acceptance allow_registration_without_qualification refund_policy_percent
+             use_wca_registration guests_per_registration_limit venue contact force_comment_in_registration use_wca_registration external_registration_page guests_entry_fee_lowest_denomination guest_entry_status information],
+    methods: %w[registration_opened? main_event_id number_of_bookmarks using_stripe_payments? uses_qualification? uses_cutoff?],
+    include: %w[tabs],
+  }.freeze
+
   def show
     competition = competition_from_params
-    render json: competition
+
+    if stale?(competition)
+      render json: competition.as_json(COMPETITION_INFO_SERIALIZE_OPTIONS)
+    end
   end
 
   def schedule

WcaOnRails/app/models/competition.rb

@@ -379,6 +379,10 @@ def registration_full?
     competitor_limit_enabled? && registrations.accepted_and_paid_pending_count >= competitor_limit
   end
 
+  def number_of_bookmarks
+    bookmarked_users.count
+  end
+
   def country
     Country.c_find(self.countryId)
   end
@@ -1911,7 +1915,10 @@ def url
   }.freeze
 
   def serializable_hash(options = nil)
-    json = super(DEFAULT_SERIALIZE_OPTIONS.merge(options || {}))
+    # This looks weird, but we need the 'deeper_merge' method to handle arrays inside hashes.
+    #   In turn, the 'deeper_merge' library has a quirk that even though it doesn't use the ! naming convention,
+    #   it tries to modify the source array in-place. This is not cool so we need to circumvent by duplicating.
+    json = super(DEFAULT_SERIALIZE_OPTIONS.deep_dup.deeper_merge(options || {}))
     # Fallback to the default 'serializable_hash' method, but always include our
     # custom 'class' attribute.
     # We can't put that in our DEFAULT_SERIALIZE_OPTIONS because the 'class'