Rename sessions generator to authentication generator (rails#52435)

Sessions is only one part of the equation. We also have users. And will
have other elements too.

Author: dhh

railties/lib/rails/generators/rails/authentication/USAGE

@@ -0,0 +1,6 @@
+Description:
+    Generates a basic authentication system with users and sessions.
+
+Example:
+    `bin/rails generate authentication`
+

railties/lib/rails/generators/rails/sessions/sessions_generator.rb renamed to railties/lib/rails/generators/rails/authentication/authentication_generator.rb

@@ -2,8 +2,8 @@
 
 module Rails
   module Generators
-    class SessionsGenerator < Base # :nodoc:
-      def create_session_files
+    class AuthenticationGenerator < Base # :nodoc:
+      def create_files
         template "models/session.rb", File.join("app/models/session.rb")
         template "models/user.rb", File.join("app/models/user.rb")
         template "models/current.rb", File.join("app/models/current.rb")

railties/lib/rails/generators/rails/sessions/templates/controllers/concerns/authentication.rb renamed to railties/lib/rails/generators/rails/authentication/templates/controllers/concerns/authentication.rb

@@ -2,9 +2,9 @@
 
 require "generators/generators_test_helper"
 require "rails/generators/rails/app/app_generator"
-require "rails/generators/rails/sessions/sessions_generator"
+require "rails/generators/rails/authentication/authentication_generator"
 
-class SessionsGeneratorTest < Rails::Generators::TestCase
+class AuthenticationGeneratorTest < Rails::Generators::TestCase
   include GeneratorsTestHelper
 
   def setup
@@ -16,11 +16,11 @@ def teardown
     Rails.application = Rails.application.instance
   end
 
-  def test_session_generator
+  def test_authentication_generator
     self.class.tests Rails::Generators::AppGenerator
     run_generator([destination_root])
 
-    self.class.tests Rails::Generators::SessionsGenerator
+    self.class.tests Rails::Generators::AuthenticationGenerator
     run_generator
 
     assert_file "app/models/user.rb"