Add Sonarr v3 removal to the v7.0 upgrade guide

docs/cli/config/config-create.md

@@ -33,7 +33,7 @@ recyclarr config create
 recyclarr config create --path ~/myconfig.yml
 ```
 
-### `-t|--template`
+### `-t|--template` {#template}
 
 Create configuration [from templates][templates] instead of the built-in starter YAML configuration.
 This option may be specified multiple times. Each template specified will yield 1 new YAML file

docs/upgrade-guide/v7.0.md

@@ -44,3 +44,32 @@ for you.
 [net8]: https://learn.microsoft.com/en-us/dotnet/core/compatibility/core-libraries/8.0/getfolderpath-unix
 [mig]: ../behavior/migration-system.md
 [cmd]: ../cli/migrate.md
+
+### Removed Sonarr v3 Support
+
+With this release, Sonarr version 3 support has been completely dropped. The most impactful aspect
+of this is the removal of Release Profile syncing. If you're already running Sonarr v4, then there
+should be no action required. For those still using Sonarr v3, you have two options:
+
+#### Option 1: Stay on Recyclarr v6.0
+
+If you prefer to stay on Sonarr version 3.0, then you should not upgrade to this release of
+Recyclarr. For now, stay on the latest release of Recyclarr v6.0. It is recommended that you
+eventually upgrade your instances of Sonarr, however, so that you can continue using the latest
+release of Recyclarr. Older versions of Recyclarr stop working once there are breaking changes in
+the Trash Guides.
+
+#### Option 2: Upgrade your instances of Sonarr
+
+1. Upgrade your v3 instance(s) of Sonarr to v4.0 or higher. **It is <ins>your</ins> responsibility
+   to follow proper upgrade procedure** (e.g. do proper backups), as this is outside the scope of
+   Recyclarr itself.
+
+1. Go through all of your configuration YAML files and replace usage of `release_profiles` with
+   `custom_formats`. See the [Configuration Reference][ref] page for details. With Sonarr v4, you
+   will also have access to Sonarr configuration templates. You may decide to replace your
+   hand-written Sonarr v3 configuration with a pre-made template instead. See the [`config
+   create`][config_create] command for details on how to list available templates and create them.
+
+[ref]: /yaml/config-reference/index.md
+[config_create]: ../cli/config/config-create.md#template