Upgrade to Rails 7.0 and apply new framework defaults

* Remove `send_stream` method pulled in before upgrading Rails
* Remove spring, it is no longer included by default for new apps
* Remove deprecated options from environments
* Remove old asset paths and workarounds no longer needed
* Remove unnecessary `OAUTH_10_SUPPORT` const, LTI still uses OAuth 1.0
* Dump schema with new defaults (and specify precision for timestamps where needed)

config/application.rb

@@ -13,7 +13,7 @@ require 'telegraf/rails'
 module CodeOcean
   class Application < Rails::Application
     # Initialize configuration defaults for originally generated Rails version.
-    config.load_defaults 6.1
+    config.load_defaults 7.0
 
     # Configuration for the application, engines, and railties goes here.
     #
@@ -29,12 +29,12 @@ module CodeOcean
     # config.i18n.default_locale = :de
     config.i18n.available_locales = %i[de en]
 
-    extra_paths = %W[
-      #{config.root}/lib
+    extra_paths = [
+      Rails.root.join('lib'),
     ]
 
     # Add generators, they don't have a module structure that matches their directory structure.
-    extra_paths << "#{config.root}/lib/generators"
+    extra_paths << Rails.root.join('lib/generators')
 
     config.add_autoload_paths_to_load_path = false
     config.autoload_paths += extra_paths