Identity Assurance - change error behavior for essential at date element

[Torsten Lodderstedt]

as mike pegmann correctly pointed out, the current behavior (refusal to proceed) differs from core OIDC

Although OIDC core allows to define different behavior for essential and other claims, alignment with the well know behavior seems a good idea. The issues I had in mind can be coped with differently (e.g. during billing).

[Torsten Lodderstedt]

changed description to comply with OIDC default behavior in -02