2.x: add UPGRADE.md file to upgrade to v2

README.md

@@ -322,6 +322,10 @@ The `Webhook::read` function will return a `Notification` instance. Please, [exp
 - Ask a question on the [Discussions forum](https://github.com/netflie/whatsapp-cloud-api/discussions "Discussions forum")
 - To report bugs, please [open an issue](https://github.com/netflie/whatsapp-cloud-api/issues/new/choose "open an issue")
 
+## Migration to v2
+
+Please see [UPGRADE](https://github.com/netflie/whatsapp-cloud-api/blob/main/UPGRADE.md "UPGRADE") for more information on how to upgrade to v2.
+
 ## Changelog
 
 Please see [CHANGELOG](https://github.com/netflie/whatsapp-cloud-api/blob/main/CHANGELOG.md "CHANGELOG") for more information what has changed recently.

UPGRADE.md

@@ -0,0 +1,18 @@
+# Upgrade to v2
+
+All instructions to upgrade this project from one major version to the next will be documented in this file. Upgrades must be run sequentially, meaning you should not skip major releases while upgrading (fix releases can be skipped).
+
+## 1.x to 2.x
+
+# Final classes
+A lot of classes have been marked as final classes. If you have created new classes that extend any of them you will have to create new implementations. The reason for this change is to hide implementation details and avoid breaking versions in subsequent releases. Check the affected classes: https://github.com/netflie/whatsapp-cloud-api/commit/4cf094b1ff9a477eda34151a0e68fc7417950bbb
+
+# Response errors
+In previous versions when a request to WhatsApp servers failed a `GuzzleHttp\Exception\ClientException` exception was thrown. From now on a `Netflie\WhatsAppCloudApi\Response\ResponseException` exception will be thrown.
+
+# Client
+`Client::sendRequest(Request $request)` has been refactored to `Client::sendMessage(Request\RequestWithBody $request)`
+
+# Request
+Request class has been refactored: https://github.com/netflie/whatsapp-cloud-api/commit/17f76e90122d245aace6640a1f8766fb77c29ef6#diff-74d71c4d1f9d84b9b0d946ca96eb875274f95d60611611d84cc01cdf6ed04021L5
+