minor #495 Inform about potential BC break after response code change…

… (Zales0123)

This PR was merged into the 1.10 branch.

Discussion
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| Q               | A
| --------------- | -----
| Bug fix?        | no
| New feature?    | no
| BC breaks?      | no
| Deprecations?   | no
| Related tickets | 
| License         | MIT

Btw, nothing changed in the `UPGRADE` file since 1.7 release 😅 we should probably take care of documenting some changes between 1.7, 1.8, 1.9 and 1.10 💃


Commits
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4c77d2f Inform about potential BC break after response code change

UPGRADE.md

@@ -1,3 +1,12 @@
+## UPGRADE FOR `1.10.x`
+
+### FROM `1.9.x` to `1.10.x`
+
+- failed form response status code returned from the `ResourceController::createAction` and `ResourceController::updateAction` changed from `200` to `422`
+
+  see: https://github.com/Sylius/SyliusResourceBundle/pull/488. This is technically a bug fix, but could break the application
+  if your logic is based on this bugged previous status code  
+
 ## UPGRADE FOR `1.7.x`
 
 ### FROM `1.6.x` TO `1.7.x`