Organize sections by conformance classes

[elf-pavlik]

Looking at the sequence diagram we can see 6 conformance classes, I'd like to clarify which section applies to which conformance class.

1. End User's WebID Document
   • WebID Issuer Discovery via Link Headers
2. OpenID Provider (OP)
   • Solid-OIDC Conformance Discovery
   • Requesting the WebID Claim using a Scope Value
   • DPoP Proof Validation
   • Client ID Document
   • Token Instantiation
   • DPoP-bound OIDC ID Token
   • Validate Client Identity (redirect_uri) Client ID Document
   • PKCE
3. Client's ID Document
   • Client ID Document
4. Client
   • Requesting the WebID Claim using a Scope Value
   • Authorization Server Discovery
   • Obtaining Access Token
   • PKCE
5. Resource Server (RS)
   • Authorization Server Discovery
6. Authorization Server (AS)
   • Obtaining Access Token
   • DPoP Proof Validation
   • OIDC ID Token Validation
   • WebID Issuer Discovery via Link Headers

I'll be updating the list above.

Besides tidying up the sections, we could add something similar to https://www.w3.org/TR/websub/#conformance-classes