upgrade guide (#2325)

* upgrade from ACA 2.4.0 to 2.5.0

* * minor changes

* * remove aca prefix

docs/upgrade-guide/README.md

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+---
+Title: Upgrade guides
+Github only: true
+---
+
+# Upgrade guides
+
+Below are links to the upgrade guides notes for released versions
+
+## Contents
+
+- [Upgrade from v2.4.o to v2.5.0](/upgrade-guide/upgrade24-45)

docs/upgrade-guide/upgrade24-45.md

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+---
+Title: Upgrade from v2.4.0 to v2.5.0
+Github only: true
+---
+
+# Upgrade from v2.4.0 to v2.5.0
+
+This guide explains how to upgrade your ACA v2.4.0 project to work with v2.5.0.
+
+Do not skip this task, if you want your application to be updated to a most recent version of ACA. 
+Upgrades of multiple versions of ACA cannot be done in one step only, but should follow the chain of sequential updates. 
+
+**Note:** the steps described below might involve making changes
+to your code. If you are working with a versioning system then you should
+commit any changes you are currently working on. If you aren't using versioning
+then be sure to make a backup copy of your project before going ahead with the
+upgrade.
+
+### Search Forms
+We released a new feature called search forms. It would allow the user to set up numerous search configurations, and it could be extended from the extension. 
+
+![](../images/search-layout-2.5.0.png)
+
+We moved the search object to [`app.extension.json`](https://github.com/Alfresco/alfresco-content-app/blob/v2.5.0/src/assets/app.extensions.json#L1181) from [`app.config.json`](https://github.com/Alfresco/alfresco-content-app/blob/v2.4.0/src/app.config.json#L192) in order to enable extendable search forms.
+
+#### How to opt to this?
+ If you don't have any search override, you can just remove the [`search`](https://github.com/Alfresco/alfresco-content-app/blob/v2.4.0/src/app.config.json#L192) configuration from app.config.json
+
+#### What if search configuration is customised?
+ The customised configuration should be moved to the custom extension own by you. [check here](/tutorials/search-form)
+ 
+#### How can I know if search setup is customised?
+ Just compare your app.config search object with [old configuration](https://github.com/Alfresco/alfresco-content-app/blob/v2.4.0/src/app.config.json#L192)
+ 
+### See also
+  - [How to extend The Search Form](/tutorials/search-form)