Add some words about the Radicale integration

docs/admin/configuration/radicale-integration.md

@@ -0,0 +1,70 @@
+---
+sidebar_position: 12
+id: radicale-integration
+title: Calendar and Contacts Integration with Radicale
+description: "How to enable Calendar and Contacts integration via Radicale in OpenCloud."
+---
+
+OpenCloud is able to act as an authenticating reverse proxy for the open-source
+CalDAV and CardDAV Server [Radicale](https://radicale.org). With that, users
+get a calender- and contacts server out of the box with OpenCloud that can be
+used with a wide selection of desktop- and mobile clients without hassle.
+
+The `opencloud_full` deployment example already contains all the required pieces to
+setup the integration. This guide explains the required steps to achieve that.
+
+
+:::note
+The calendar and contacts feature is - until further notice - intended for
+non-customers, i.e. please note that it is not covered under our business
+license, and we do not provide professional support for it. This means that
+this feature is maintained and supported on best effort without warranty.
+:::
+
+
+## Setting up Calendar and Contacts Integration with Radicale
+
+To use this feature you need at least OpenCloud Version 2.3.0. Earlier releases lack
+some of the required features. This guide assumes that you already have a running
+deployment based on the `opencloud_full` deployment example.
+
+### 1. Configure the `.env` file to deploy Radicale
+
+In the root directory of the `opencloud_full` deployment example, usually `opencloud/deployments/examples/opencloud_full`, 
+remove the `#` symbol from the line:
+
+```
+#RADICALE=:radicale.yml
+```
+
+### 2. Update the deployment
+
+```
+docker compose up -d
+```
+
+This will launch an additional container (called `radicale`) using the
+`opencloudeu/radicale` container image and reconfigure the OpenCloud instance
+to automatically forward all authenticated traffic on
+`https://<your.opencloud.domain>/caldav` and
+`https://<your.opencloud.admin>/carddav` to the radicale container adding
+information about the authenticated users.
+
+Radicale is configured to automatically create default calendar and address book for every authenticated user.
+
+## Accessing the Calendar and Address Book
+
+Users should now be able to access their address book and calendar with any
+capable CalDAV/CardDAV software (OpenCloud does currently not provide any UI
+to access them).
+
+As very few clients currently support authentication via OpenID Connect you can use
+the "App Token" feature in the user's settings page to generate an application specific
+password that can be used for authentication in most existing CalDAV/CardDAV clients.
+
+As OpenCloud implements support for the `.well-known/carddav` and `.well-known/caldav`
+endpoint. Many clients are able to automatically discover existing calendars and
+address books. So the only thing that is needed for those clients to work is
+to set `https://<your.opencloud.domain>` as the target URL for calendars and
+address books together with the OpenCloud username as the username and the
+generated app token as the password for authentication.