feat(migrate): add AddIndexOnPostsUserId, down and AddSlugToPosts

examples/blog/db/migrate/20260907000009_add_index_on_posts_user_id.rb

@@ -0,0 +1,9 @@
+class AddIndexOnPostsUserId < Prism::Orm::Migration
+  def up
+    add_index :posts, :user_id
+  end
+
+  def down
+    remove_index :posts, :user_id
+  end
+end

examples/blog/db/migrate/20260907000010_add_slug_to_posts.rb

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+class AddSlugToPosts < Prism::Orm::Migration
+  def up
+    # add_column's own default ('') would leave every existing row with the
+    # SAME empty slug, which the unique index below would reject the moment
+    # a second existing post tried to keep it - so every existing row gets
+    # a real, distinct slug backfilled BEFORE the index goes on, the same
+    # slugify Post.create_with_unique_slug uses for new rows (this runs at
+    # the store level, not through the Post model - db:migrate does not
+    # load app/models, see Prism::Cli#db_migrate).
+    add_column :posts, :slug, default: ''
+    backfill_unique_slugs
+    add_index :posts, :slug, unique: true
+  end
+
+  def down
+    remove_index :posts, :slug
+    remove_column :posts, :slug
+  end
+
+  private
+
+  def backfill_unique_slugs
+    seen = {}
+    store.all(:posts).each do |row|
+      base = slugify(row['title'])
+      slug = base
+      suffix = 1
+      while seen.key?(slug)
+        suffix += 1
+        slug = "#{base}-#{suffix}"
+      end
+      seen[slug] = true
+      store.update(:posts, row['id'], 'slug' => slug)
+    end
+  end
+
+  def slugify(title)
+    base = title.to_s.downcase.gsub(/[^a-z0-9]+/, '-').gsub(/\A-+|-+\z/, '')
+    base.empty? ? 'post' : base
+  end
+end

examples/blog/db/migrate/20260907000011_add_featured_to_posts.rb

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+class AddFeaturedToPosts < Prism::Orm::Migration
+  def up
+    add_column :posts, :featured, default: false
+  end
+
+  def down
+    remove_column :posts, :featured
+  end
+end

examples/blog/db/migrate/20260907000012_add_confirmed_at_to_users.rb

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+class AddConfirmedAtToUsers < Prism::Orm::Migration
+  def up
+    add_column :users, :confirmed_at, :datetime, default: nil
+  end
+
+  def down
+    remove_column :users, :confirmed_at
+  end
+end

examples/blog/db/migrate/20260907000013_add_position_to_posts.rb

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+class AddPositionToPosts < Prism::Orm::Migration
+  def up
+    add_column :posts, :position
+  end
+
+  def down
+    remove_column :posts, :position
+  end
+end

examples/blog/db/migrate/20260908000001_add_composite_index_on_posts_featured_and_position.rb

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+class AddCompositeIndexOnPostsFeaturedAndPosition < Prism::Orm::Migration
+  def up
+    add_index :posts, %i[featured position]
+  end
+
+  def down
+    remove_index :posts, %i[featured position]
+  end
+end

examples/blog/db/migrate/20260908000002_add_giveaway_slots_to_posts.rb

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+class AddGiveawaySlotsToPosts < Prism::Orm::Migration
+  def up
+    # No default (nil) on purpose - nil means "not a giveaway post" (see
+    # Post#giveaway?), distinct from 0 ("was a giveaway, now sold out
+    # forever"). A post created before this migration, or one nobody ever
+    # opted into the giveaway field for, reads back as nil either way.
+    add_column :posts, :giveaway_slots, :integer
+  end
+
+  def down
+    remove_column :posts, :giveaway_slots
+  end
+end

examples/blog/db/migrate/20260908000003_create_claims.rb

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+class CreateClaims < Prism::Orm::Migration
+  def up
+    create_table :claims do |t|
+      t.integer :post_id
+      t.integer :user_id
+      t.datetime :deleted_at
+      t.timestamps
+    end
+    # Belt and braces with Claim's own `validates :user_id, uniqueness:
+    # { scope: :post_id }`: the model-level check only ever sees rows this
+    # same process/transaction can already read, whereas this unique index
+    # is enforced by Store#validate_unique_indexes inside the very same
+    # transaction the insert itself runs in (see Store#insert), so it
+    # still catches a duplicate claim even in the hypothetical case of two
+    # inserts racing without going through Post#with_lock first.
+    add_index :claims, %i[post_id user_id], unique: true
+  end
+
+  def down
+    drop_table :claims
+  end
+end

examples/blog/db/migrate/20260908000004_add_claims_count_to_posts.rb

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+class AddClaimsCountToPosts < Prism::Orm::Migration
+  def up
+    add_column :posts, :claims_count, :integer, default: 0
+  end
+
+  def down
+    remove_column :posts, :claims_count
+  end
+end