Update CHANGELOG and UPGRADING

CHANGELOG.md

@@ -5,6 +5,7 @@
 
 ### Added
 
+- [#2254](https://github.com/slimphp/Slim/pull/2254) Added Middleware\ContentLength
 - [#2166](https://github.com/slimphp/Slim/pull/2166) Added Middleware\OutputBuffering
 
 ### Deprecated
@@ -13,6 +14,8 @@
 
 ### Removed
 
+- [#2254](https://github.com/slimphp/Slim/pull/2254) `addContentLengthHeader` setting is removed
+- [#2166](https://github.com/slimphp/Slim/pull/2166) `outputBuffering` setting is removed
 - [#2067](https://github.com/slimphp/Slim/pull/2067) Remove App::VERSION
 - [#2078](https://github.com/slimphp/Slim/pull/2078) Remove App::subRequest()
 - [#2098](https://github.com/slimphp/Slim/pull/2098) Remove CallableResolverTrait

UPGRADING.md

@@ -1,9 +1,11 @@
 # How to upgrade
 
+* [2254] - You need to add the `Middleware\ContentLength` middleware if you want Slim to add this automatically.
 * [2166] - You need to add the `Middleware\OutputBuffering` middleware to capture echo'd or var_dump'd output from your code.
 * [2098] - You need to add the App's router to the container for a straight upgrade. If you've created your own router factory in the container though, then you need to set it into the $app.
 * [2102] - You must inject custom route invocation strategy with `$app->getRouter()->setDefaultInvocationStrategy($myStrategy)`
 
+[2254]: https://github.com/slimphp/Slim/pull/2254
 [2166]: https://github.com/slimphp/Slim/pull/2166
 [2098]: https://github.com/slimphp/Slim/pull/2098
 [2102]: https://github.com/slimphp/Slim/pull/2102