update documentation 16-08-2023

Signed-off-by: Karel van Klink karel.vanklink@geant.org

docs/admin_guide/index.md

+# About this section
+
+All the information regarding modeling, workflows and Ansible mechanics are described in this section.
+Next to this, also troubleshooting and maintenance are included.
+
+The structure is:
+
+- {term}`WFO`
+  - Modelling
+  - Workflow
+  - Maintenance
+  - Troubleshoot
+- Ansible
+  - Design
+  - Low level description
+  - Troubleshoot