rails: update framework files and settings to 7.0.

* Update framework files with `bin/rails app:update`.
* Update to use new Rails 7.0 default settings, except for a couple
  things regarding new cookie and cache formats that would prevent us
  from rolling back to Rails 6.1 if necessary.

config/initializers/cors.rb

@@ -7,9 +7,9 @@
 
 # Rails.application.config.middleware.insert_before 0, Rack::Cors do
 #   allow do
-#     origins 'example.com'
+#     origins "example.com"
 #
-#     resource '*',
+#     resource "*",
 #       headers: :any,
 #       methods: [:get, :post, :put, :patch, :delete, :options, :head]
 #   end