Add `pinned_at` to answers

app/models/answer.rb

@@ -14,6 +14,8 @@ class Answer < ApplicationRecord
   validates :question_id, uniqueness: { scope: :user_id }
   # rubocop:enable Rails/UniqueValidationWithoutIndex
 
+  scope :pinned, -> { where.not(pinned_at: nil) }
+
   SHORT_ANSWER_MAX_LENGTH = 640
 
   # rubocop:disable Rails/SkipsModelValidations
@@ -56,4 +58,6 @@ class Answer < ApplicationRecord
   end
 
   def long? = content.length > SHORT_ANSWER_MAX_LENGTH
+
+  def pinned? = pinned_at.present?
 end

db/migrate/20230128233136_add_pinned_at_to_answers.rb

@@ -0,0 +1,8 @@
+# frozen_string_literal: true
+
+class AddPinnedAtToAnswers < ActiveRecord::Migration[6.1]
+  def change
+    add_column :answers, :pinned_at, :timestamp
+    add_index :answers, %i[user_id pinned_at]
+  end
+end

db/schema.rb

@@ -48,8 +48,10 @@ ActiveRecord::Schema.define(version: 2023_02_12_181044) do
     t.datetime "created_at"
     t.datetime "updated_at"
     t.integer "smile_count", default: 0, null: false
+    t.datetime "pinned_at"
     t.index ["question_id"], name: "index_answers_on_question_id"
     t.index ["user_id", "created_at"], name: "index_answers_on_user_id_and_created_at"
+    t.index ["user_id", "pinned_at"], name: "index_answers_on_user_id_and_pinned_at"
   end
 
   create_table "appendables", force: :cascade do |t|