Solid OIDC Client Identifiers

[csarven]

In #clientids:

Mention the two options where/why client application may be a URI that can be dereferenced or not. Refer to section #clientids-oidc for requirements on when non-dereferencable identifier is used.

Consider restructuring this section to have subsections in this order 1) Non-dereferenceable identifier 2) Dereferenceable identifier 3) Client ID Document