Merge pull request rails#17076 from yuki24/write-doc-for-rescue-responses

Add documentation about rescue_responses in Configuring [ci skip]

Author: Zachary Scott

guides/source/configuring.md

@@ -364,6 +364,29 @@ encrypted cookies salt value. Defaults to `'signed encrypted cookie'`.
   method should be performed on the parameters. See [Security Guide](security.html#unsafe-query-generation)
   for more information. It defaults to true.
 
+* `config.action_dispatch.rescue_responses` configures what exceptions are assigned to an HTTP status. It accepts a hash and you can specify pairs of exception/status. By default, this is defined as:
+
+  ```ruby
+  config.action_dispatch.rescue_responses = {
+     'ActionController::RoutingError'             => :not_found,
+     'AbstractController::ActionNotFound'         => :not_found,
+     'ActionController::MethodNotAllowed'         => :method_not_allowed,
+     'ActionController::UnknownHttpMethod'        => :method_not_allowed,
+     'ActionController::NotImplemented'           => :not_implemented,
+     'ActionController::UnknownFormat'            => :not_acceptable,
+     'ActionController::InvalidAuthenticityToken' => :unprocessable_entity,
+     'ActionDispatch::ParamsParser::ParseError'   => :bad_request,
+     'ActionController::BadRequest'               => :bad_request,
+     'ActionController::ParameterMissing'         => :bad_request,
+     'ActiveRecord::RecordNotFound'               => :not_found,
+     'ActiveRecord::StaleObjectError'             => :conflict,
+     'ActiveRecord::RecordInvalid'                => :unprocessable_entity,
+     'ActiveRecord::RecordNotSaved'               => :unprocessable_entity
+  }
+  ```
+
+  Any execptions that are not configured will be assigned to 500 Internal server error.
+
 * `ActionDispatch::Callbacks.before` takes a block of code to run before the request.
 
 * `ActionDispatch::Callbacks.to_prepare` takes a block to run after `ActionDispatch::Callbacks.before`, but before the request. Runs for every request in `development` mode, but only once for `production` or environments with `cache_classes` set to `true`.