Use new dummy app tailwind in admin gem

admin/Rakefile

@@ -5,6 +5,7 @@ require 'rake'
 require 'rake/testtask'
 require 'rspec/core/rake_task'
 require 'spree/testing_support/dummy_app/rake_tasks'
+require 'solidus_admin/testing_support/dummy_app/rake_tasks'
 require 'bundler/gem_tasks'
 
 namespace :tailwindcss do

admin/spec/spec_helper.rb

@@ -29,11 +29,7 @@
  mount Spree::Core::Engine, at: '/'
 end
 
-unless SolidusAdmin::Engine.root.join('app/assets/builds/solidus_admin/tailwind.css').exist?
- Dir.chdir(SolidusAdmin::Engine.root) do
- system 'bundle exec rake tailwindcss:build' or abort 'Failed to build Tailwind CSS'
- end
-end
+require "solidus_admin/testing_support/admin_assets"
 
 # RAILS
 require "rspec/rails"
@@ -111,6 +107,9 @@
  config.before do
  Rails.cache.clear
  end
+ config.define_derived_metadata(file_path: %r{spec/features}) do |metadata|
+ metadata[:solidus_admin] = true
+ end
 
  config.include FactoryBot::Syntax::Methods