refactor: ⚡ Username and slug unique indexes, before actions for set link and user

confirm_password_validation around action, unnecessary helpers removed, rubocop-rails suggestions applied

Add username index and unique slug index migrations

db/migrate/20210615193108_add_username_index_to_users.rb

@@ -0,0 +1,7 @@
+# frozen_string_literal: true
+
+class AddUsernameIndexToUsers < ActiveRecord::Migration[5.2]
+  def change
+    add_index :users, :username, unique: true
+  end
+end

db/migrate/20210615200050_unique_slug_index.rb

@@ -0,0 +1,8 @@
+# frozen_string_literal: true
+
+class UniqueSlugIndex < ActiveRecord::Migration[5.2]
+  def change
+    remove_index :links, column: :slug
+    add_index :links, :slug, unique: true
+  end
+end

db/schema.rb

@@ -1,5 +1,3 @@
-# frozen_string_literal: true
-
 # This file is auto-generated from the current state of the database. Instead
 # of editing this file, please use the migrations feature of Active Record to
 # incrementally modify your database, and then regenerate this schema definition.
@@ -12,27 +10,29 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema.define(version: 20_210_614_114_837) do
+ActiveRecord::Schema.define(version: 2021_06_15_200050) do
+
   # These are extensions that must be enabled in order to support this database
-  enable_extension 'plpgsql'
+  enable_extension "plpgsql"
 
-  create_table 'links', force: :cascade do |t|
-    t.string 'slug', null: false
-    t.text 'url'
-    t.integer 'click_counter', default: 0
-    t.datetime 'created_at', null: false
-    t.datetime 'updated_at', null: false
-    t.bigint 'user_id'
-    t.index ['slug'], name: 'index_links_on_slug'
-    t.index ['user_id'], name: 'index_links_on_user_id'
+  create_table "links", force: :cascade do |t|
+    t.string "slug", null: false
+    t.text "url"
+    t.integer "click_counter", default: 0
+    t.datetime "created_at", null: false
+    t.datetime "updated_at", null: false
+    t.bigint "user_id"
+    t.index ["slug"], name: "index_links_on_slug", unique: true
+    t.index ["user_id"], name: "index_links_on_user_id"
   end
 
-  create_table 'users', force: :cascade do |t|
-    t.string 'username'
-    t.string 'password_digest'
-    t.datetime 'created_at', null: false
-    t.datetime 'updated_at', null: false
+  create_table "users", force: :cascade do |t|
+    t.string "username"
+    t.string "password_digest"
+    t.datetime "created_at", null: false
+    t.datetime "updated_at", null: false
+    t.index ["username"], name: "index_users_on_username", unique: true
   end
 
-  add_foreign_key 'links', 'users'
+  add_foreign_key "links", "users"
 end