Update Kubernetes deployments docs (#1339)

* doc: Add a note about database migrations for AKS

* doc: Add a note about db migration to General k8s docs

* doc: Add a note about k8s version upgrades for AKS

* doc: Fix spelling

doc/content/the-things-stack/host/kubernetes/azure/upgrading/_index.md

@@ -0,0 +1,37 @@
+---
+title: "Upgrading"
+description: ""
+weight: 4
+---
+
+This page describes the steps for upgrading {{% tts %}} on Azure Kubernetes Service.
+
+<!--more-->
+
+## Database Migration
+
+{{% tts %}} database schema is managed between minor versions using database migrations.
+
+{{< note >}}
+User are informed of required migrations for each version via the [Release Notes](https://www.thethingsindustries.com/docs/whats-new/). It’s mandatory to run required database migrations for {{% tts %}} to function properly.
+{{</ note >}}
+
+To migrate the database during an upgrade set the respective Terraform variables to `true`.
+
+| Service | Variable         |
+| ------- | ---------------- |
+| IS      | `is-db-migrate`  |
+| NOC     | `noc-db-migrate` |
+
+{{< note >}}
+For example to migrate Identity Server and Network Operations Center databases run the following command.
+
+```bash
+$ terraform apply -var='is-db-migrate=true' -var='noc-db-migrate=true'
+```
+
+{{</ note >}}
+
+## Kubernetes version upgrade
+
+AKS Kubernetes version upgrades have to be performed sequentially for each minor version. For example to upgrade from `1.25` to `1.27` it's necessary to upgrade to version `1.26` first as an intermediate step. For more information refer to the [official documentation](https://learn.microsoft.com/en-us/azure/aks/supported-kubernetes-versions).

doc/content/the-things-stack/host/kubernetes/generic/database-migrations/_index.md

@@ -4,7 +4,7 @@ description: ""
 weight: 7
 ---
 
-{{% tts %}} database entries are managed between minor versions using database migrations.
+{{% tts %}} database schema is managed between minor versions using database migrations.
 
 User are informed of required migrations for each version via the [Release Notes](https://www.thethingsindustries.com/docs/whats-new/). It's mandatory to run required database migrations for {{% tts %}} to function properly.
 
@@ -14,6 +14,28 @@ This page describes the steps for performing database operations on a {{% tts %}
 
 ## General Procedure
 
+Set the respective Helm chart values to `true` to perform database migrations during Helm chart upgrade.
+
+| Service | Variable                     |
+| ------- | ---------------------------- |
+| IS      | `is.database.migrate`        |
+| NOC     | `noc.store.database.migrate` |
+
+{{< note >}}
+For example to migrate Identity Server use the following config.
+
+```yaml
+is:
+  database:
+    migrate: true
+```
+
+{{</ note >}}
+
+Remember to unset the value after the upgrade is done.
+
+## Manual Procedure
+
 1. Delete current Jobs (if any).
 
 ```bash