How-to AAI general

Every day, we stumble over the same old problems of VO managers and users. With this MR, we could try to catch some of the most frequent problems by an as-short-as-can-be howto:

• A) for end users in normal login
• B) for users being invited to groups
• C) for VO managers

Once finished, this page should be linked to in basically every ticket, especially once a new VO is created. Also hifis.net and login.helmholtz.de should link there.

---

• Review here

---

Related:

• https://codebase.helmholtz.cloud/hifis/overall/ux/-/issues/7#note_6148216
• https://codebase.helmholtz.cloud/hifis/overall/ux/-/issues/7#note_6148262
• https://codebase.helmholtz.cloud/hifis/overall/ux/-/issues/7#note_6148264

---

In this MR:

• Created the simple page
• Clean up: moved the mixture that ended up as old users-how-to page, and split that to
  • a) further information (might even be deleted), and
  • b) OIDC agent related stuff.

docs/helmholtz-aai/README.md

@@ -6,12 +6,13 @@ This is the technical and administrative documentation on Helmholtz AAI, built a
     For a high-level representation, have a look at the [Helmholtz AAI Homepage](https://hifis.net/aai) on hifis.net.
 
 Here we describe all you need to know about 
-[joining as a user](howto-users.md), 
+[basic steps for end users and group managers](howto-aai.md),
 [registering a Virtual Organisation (VO)](howto-vos.md), 
 [managing groups in VOs](howto-vo-management.md),
 [registering a service](howto-services.md),
 [joining as an identity provider](howto-idps.md), or
-[using the AAI capabilities to authorise users and user groups](howto-authorise-users.md) for fine-grained access to your service(s).
+[using the AAI capabilities to authorise users and user groups](howto-authorise-users.md) for fine-grained access to your service(s),
+and more (see menu).
 
 We further describe our [goals](#goals), [technology](concepts.md), and [policies](policies/README.md),
 and give further organisational information (see menu).