Add internal title for exercise

The internal title is designed to provide an alternative title for teachers. It is not exposed to learners.

db/migrate/20231013194635_add_internal_title_to_exercises.rb

@@ -0,0 +1,8 @@
+# frozen_string_literal: true
+
+class AddInternalTitleToExercises < ActiveRecord::Migration[7.0]
+  def change
+    add_column :exercises, :internal_title, :string
+    add_index :exercises, :internal_title, using: :gin, opclass: :gin_trgm_ops
+  end
+end

db/schema.rb

@@ -10,7 +10,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema[7.0].define(version: 2023_09_20_094122) do
+ActiveRecord::Schema[7.0].define(version: 2023_10_13_194635) do
   # These are extensions that must be enabled in order to support this database
   enable_extension "pg_trgm"
   enable_extension "pgcrypto"
@@ -248,8 +248,10 @@ ActiveRecord::Schema[7.0].define(version: 2023_09_20_094122) do
     t.boolean "unpublished", default: false
     t.datetime "submission_deadline"
     t.datetime "late_submission_deadline"
+    t.string "internal_title"
     t.index ["id"], name: "index_exercises_on_id"
     t.index ["id"], name: "index_unpublished_exercises", where: "(NOT unpublished)"
+    t.index ["internal_title"], name: "index_exercises_on_internal_title", opclass: :gin_trgm_ops, using: :gin
     t.index ["title"], name: "index_exercises_on_title", opclass: :gin_trgm_ops, using: :gin
   end