docs: 1.9 upgrade guide (#3915)

* wip

* change to minor

* Add breaking change explanation

* Update docs/content/upgrade-guides/medusa-core/1-9-0.md

Co-authored-by: Shahed Nasser <shahednasser@gmail.com>

* Update docs/content/upgrade-guides/medusa-core/1-9-0.md

Co-authored-by: Shahed Nasser <shahednasser@gmail.com>

* Update 1-9-0.md

---------

Co-authored-by: Shahed Nasser <shahednasser@gmail.com>

docs/content/upgrade-guides/medusa-core/1-9-0.md

@@ -0,0 +1,49 @@
+---
+description: 'Actions Required for v.1.9.0'
+sidebar_custom_props:
+  iconName: 'server-stack-solid'
+---
+
+# v1.9.0
+
+Version 1.9.0 of Medusa introduces database schema changes which require running the migrations command. Additionally, it ships with a minor breaking change to the events system.
+
+## Overview​
+
+This release introduces a new column `metadata` on Sales Channels. It is required to run migrations to ensure your backend works as expected.
+
+This release also comes with a breaking change to the events system. It is required to update your event bus packages to ensure events are handled correctly.
+
+In the core `EventBusService`, a check has been introduced to only insert staged jobs (in other words, fire events), if there are subscribers to it.
+
+---
+
+## How to Update
+
+Run the following command in the root directory of your Medusa Backend to update the core:
+
+```bash npm2yarn
+npm install @medusajs/medusa@1.9.0
+```
+
+Then, update your event bus dependency. If you are using an official package, run one of these two commands based on the package you have installed:
+
+```bash npm2yarn
+npm install @medusajs/event-bus-redis@1.8.3
+# or
+npm install @medusajs/event-bus-local@1.8.3
+```
+
+It's also recommended to update any other Medusa plugins or packages you have installed.
+
+---
+
+## Actions Required​
+
+### Run Migrations​
+
+After updating your Medusa backend and before running it, run the following command to run the latest migrations:
+
+```bash
+medusa migrations run
+```