Implement favoriting of courses

db/migrate/20200521091231_create_favorite_courses.rb

@@ -0,0 +1,13 @@
+class CreateFavoriteCourses < ActiveRecord::Migration[6.0]
+  def change
+    create_table :favorite_courses do |t|
+      t.string :number, null: false
+      t.string :semester, null: false
+      t.string :title, null: false
+      t.integer :user_id, null: false
+
+      t.timestamps
+    end
+    add_index :favorite_courses, [:number, :semester], unique: true
+  end
+end