fix(docs): Add functional.md and reference it in getting-started.md

docs/functional.md

@@ -0,0 +1,30 @@
+<!--
+SPDX-FileCopyrightText: 2025 Zentrum für Digitale Souveränität der Öffentlichen Verwaltung (ZenDiS) GmbH
+SPDX-License-Identifier: Apache-2.0
+-->
+
+<h1>Functional configuration</h1>
+
+This document addresses the available functional configuration options of an openDesk deployment.
+
+## Supported functional configuration
+
+While the openDesk applications allow a wide range of configuration options, only a small subset of them are supported by openDesk. This subset can be found in [`helmfile/environments/default/functional.yaml.gotmpl`](../helmfile/environments/default/functional.yaml.gotmpl)
+
+The following categories are available. Each category contains a set of options to tailor your openDesk deployment to your needs. Please find the actual options including inline documentation in [`functional.yaml.gotmpl`](../helmfile/environments/default/functional.yaml.gotmpl) itself.
+
+* Administrative options (`functional.admin.*`): Options affecting the IAM administrator role (users that are member of the LDAP group `Domain Admins`) of openDesk.
+* Authentication options (`functional.authentication.*`): Authentication related settings, e.g. define additional [OIDC](https://en.wikipedia.org/wiki/OpenID#OpenID_Connect_(OIDC)) clients or scopes.
+* External Services options (`functional.externalServices.*`): Settings controlling externally available services like APIs.
+* Filestore options (`functional.filestore.*`): Configuration options for the filestore component of openDesk, like default storage quota or file sharing options.
+* Data Protection options (`functional.dataProtection.*`): Data protection related settings.
+* Portal options (`functional.portal.*`): Options to customize the openDesk portal, e.g. if the login dialog should be enforced.
+* Chat options (`functional.chat.*`): Configuration options for the chat component of openDesk.
+* Migration options (`functional.migration.*`): Helpful setting(s) for migration scenarios.
+
+## Customization of functional options
+
+In case the options from [`functional.yaml.gotmpl`](../helmfile/environments/default/functional.yaml.gotmpl) are not sufficient, you might want to look into [`customization.yaml.gotmpl`](../helmfile/environments/default/customization.yaml.gotmpl). The customizations give you control over all templating that is being done in openDesk, but be aware it is an unsupported approach, so in case you have a strong need for customizations, please let us know by opening a ticket. We will check if it is a use case that can be supported by implementing it as part of the aforementioned [`functional.yaml.gotmpl`](../helmfile/environments/default/functional.yaml.gotmpl).
+
+> **Note<br>**
+> You can not directly template your own values in the structure found in [`customization.yaml.gotmpl`](../helmfile/environments/default/customization.yaml.gotmpl), rather, you need to reference your custom value files to overwrite the openDesk defaults. In the app specific `helmfile-child.yaml.gotmpl` files, the openDesk value files are referenced first, then afterwards, the files you define in the customizations are read. 

docs/getting-started.md

@@ -20,6 +20,9 @@ This documentation lets you create an openDesk evaluation instance on your Kuber
     * [Ingress](#ingress)
     * [Container runtime](#container-runtime)
     * [Volumes](#volumes)
+  * [Customize deployment](#customize-deployment)
+    * [Functional features](#functional-features)
+    * [Features through Customization](#features-through-customization)
   * [Connectivity](#connectivity)
     * [Ports](#ports)
       * [Web-based user interface](#web-based-user-interface)
@@ -260,7 +263,9 @@ cluster:
     readWriteMany: true
 ```
 
+## Customize deployment
 
+While openDesk configures the applications with meaningful defaults, you can check [functional.md](functional.md) if you want to change these defaults to better match your use case.
 
 ## Connectivity