Add contestant categories to contests

app/models/category.rb

@@ -0,0 +1,24 @@
+# == Schema Information
+#
+# Table name: categories
+#
+#  id         :integer          not null, primary key
+#  name       :string
+#  created_at :datetime         not null
+#  updated_at :datetime         not null
+#  contest_id :integer          not null
+#
+# Indexes
+#
+#  index_categories_on_contest_id  (contest_id)
+#
+# Foreign Keys
+#
+#  contest_id  (contest_id => contests.id)
+#
+class Category < ApplicationRecord
+  belongs_to :contest
+  has_and_belongs_to_many :contestants
+
+  validates :name, presence: true
+end