Events: initial implementation

app/models/contest.rb

@@ -20,21 +20,25 @@
 #  team               :boolean          default(FALSE)
 #  created_at         :datetime         not null
 #  updated_at         :datetime         not null
+#  event_id           :integer
 #  user_id            :integer          not null
 #
 # Indexes
 #
-#  index_contests_on_slug     (slug) UNIQUE
-#  index_contests_on_user_id  (user_id)
+#  index_contests_on_event_id  (event_id)
+#  index_contests_on_slug      (slug) UNIQUE
+#  index_contests_on_user_id   (user_id)
 #
 # Foreign Keys
 #
-#  user_id  (user_id => users.id)
+#  event_id  (event_id => events.id)
+#  user_id   (user_id => users.id)
 #
 class Contest < ApplicationRecord
   extend FriendlyId
 
   belongs_to :user
+  belongs_to :event, optional: true
   has_many :categories
   has_many :completions, dependent: :destroy
   has_many :contestants, dependent: :destroy