Setup default session store internally, no longer through an application initializer

- By default the session store will be set to cookie store with
  application name as session key.
- Older apps are not affected as they will have the session store
  initializer generated by Rails in older versions, and Rails will not
  overwrite the session store if it is already set or disabled.
- But new apps will not have the initializer, instead the session store
  will be set to cookie store by default.
- Based on comment by DHH here - https://github.com/rails/rails/issues/25181#issuecomment-222312764.

2 files changed, 3 insertions, 3 deletions

diff --git a/guides/source/action_controller_overview.md b/guides/source/action_controller_overview.md
index 58362fea58..7b1138c7d4 100644
--- a/guides/source/action_controller_overview.md
+++ b/guides/source/action_controller_overview.md
@@ -362,7 +362,7 @@ If your user sessions don't store critical data or don't need to be around for l
 
 Read more about session storage in the [Security Guide](security.html).
 
-If you need a different session storage mechanism, you can change it in the `config/initializers/session_store.rb` file:
+If you need a different session storage mechanism, you can change it in an initializer:
 
 ```ruby
 # Use the database for sessions instead of the cookie-based default,
@@ -371,7 +371,7 @@ If you need a different session storage mechanism, you can change it in the `con
 # Rails.application.config.session_store :active_record_store
 ```
 
-Rails sets up a session key (the name of the cookie) when signing the session data. These can also be changed in `config/initializers/session_store.rb`:
+Rails sets up a session key (the name of the cookie) when signing the session data. These can also be changed in an initializer:
 
 ```ruby
 # Be sure to restart your server when you modify this file.
diff --git a/guides/source/configuring.md b/guides/source/configuring.md
index 34878e5c38..a283ac3e1e 100644
--- a/guides/source/configuring.md
+++ b/guides/source/configuring.md
@@ -142,7 +142,7 @@ defaults to `:debug` for all environments. The available log levels are: `:debug
 
 * `config.public_file_server.enabled` configures Rails to serve static files from the public directory. This option defaults to `true`, but in the production environment it is set to `false` because the server software (e.g. NGINX or Apache) used to run the application should serve static files instead. If you are running or testing your app in production mode using WEBrick (it is not recommended to use WEBrick in production) set the option to `true.` Otherwise, you won't be able to use page caching and request for files that exist under the public directory.
 
-* `config.session_store` is usually set up in `config/initializers/session_store.rb` and specifies what class to use to store the session. Possible values are `:cookie_store` which is the default, `:mem_cache_store`, and `:disabled`. The last one tells Rails not to deal with sessions. Custom session stores can also be specified:
+* `config.session_store` specifies what class to use to store the session. Possible values are `:cookie_store` which is the default, `:mem_cache_store`, and `:disabled`. The last one tells Rails not to deal with sessions. Defaults to a cookie store with application name as the session key. Custom session stores can also be specified:
 
     ```ruby
     config.session_store :my_custom_store