Make Quantity name unique among siblings

Remove Quantity domain - will be replaced by configurable per-domain
root Quantity, limiting selection to descendants only

app/models/quantity.rb

@@ -9,7 +9,8 @@ class Quantity < ApplicationRecord
   validate if: ->{ parent.present? } do
     errors.add(:parent, :user_mismatch) unless user == parent.user
   end
-  validates :name, presence: true, length: {maximum: type_for_attribute(:name).limit}
+  validates :name, presence: true, uniqueness: {scope: [:user_id, :parent_id]},
+    length: {maximum: type_for_attribute(:name).limit}
   validates :description, length: {maximum: type_for_attribute(:description).limit}
 
   scope :defaults, ->{ where(user: nil) }

db/migrate/20250104194343_create_quantities.rb

@@ -2,12 +2,12 @@ class CreateQuantities < ActiveRecord::Migration[7.2]
   def change
     create_table :quantities do |t|
       t.references :user, foreign_key: true
-      t.integer :domain
       t.string :name, null: false, limit: 31
       t.text :description
       t.references :parent, foreign_key: {to_table: :quantities}
 
       t.timestamps null: false
     end
+    add_index :quantities, [:user_id, :parent_id, :name], unique: true
   end
 end

db/schema.rb

@@ -13,13 +13,13 @@
 ActiveRecord::Schema[7.2].define(version: 2025_01_04_194343) do
   create_table "quantities", charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
     t.bigint "user_id"
-    t.integer "domain"
     t.string "name", limit: 31, null: false
     t.text "description"
     t.bigint "parent_id"
     t.datetime "created_at", null: false
     t.datetime "updated_at", null: false
     t.index ["parent_id"], name: "index_quantities_on_parent_id"
+    t.index ["user_id", "parent_id", "name"], name: "index_quantities_on_user_id_and_parent_id_and_name", unique: true
     t.index ["user_id"], name: "index_quantities_on_user_id"
   end