[Task](identity): change policy so projects can be created by everyone

[edda]

Task Description When this PR in Keystone is live, adjust the Elektra identity policy with matching changes. What we want to achieve is that everybody, not only domain admins, can create projects.

Sub-tasks

• [ ] change identity policy (see above Keystone change for reference)
• [ ] Verify that after the change everybody can create projects and there's no weirdness in Elektra behaviour

Related Issues

• https://github.com/sapcc/helm-charts/pull/7277
• #1386

Additional Context Add any other context or information here.