Merge branch '236-add-aai-tutorial' into 'master'

Add link to aai login tutorial

See merge request !456

_posts/2021/06/2021-06-23-how-to-helmholtz-aai.md

+---
+title: "AAI login to Helmholtz Cloud and Associated Services"
+title_image: spacex-uj3hvdfQujI-unsplash.jpg
+data: 2021-06-23
+authors:
+  - "Uwe Jandt"
+layout: blogpost
+categories:
+  - tutorial
+redirect_to:
+  - https://aai.helmholtz.de/tutorial/2021/06/23/how-to-helmholtz-aai.html
+excerpt: >
+    Pictured tutorial on usage of Helmholtz AAI login and registration procedures for Helmholtz Cloud and Associated services, using the HIFIS Events Management Platform at <a href="https://events.hifis.net">events.hifis.net</a> as an example.
+---