Migrate to draft 8

[babisRoutis]

It seems that there is a new draft (8) for the SD-JWT specification.

In general I have the impression that there are no changes to the implementation except some minor updates to the examples and the removal of the prohibition on using HMAC.

• [x] Update readme to point to new spec
• [x] Update Flat SD-JWT example. The link changed, the content of the JSON document now includes only address
• [x] Update Structured SD-JWT example. Just the link updated. Example remains the same
• [x] Update SD-JWT with recursive disclosures example. Just the link
• [x] Update Appendix 1. Example 2. Just the link
• [x] Update Appendix 2. Example 3. Just the link. I think the that example remains the same
• [x] Update Appendix 3. Example 4a. Besides the new link the JSON document was updated
• [x] Add new example for W3C VC DM 2.0
• [x] Remove the explicit prohibition on HMAC
• [x] Remove support for enveloped format

[babisRoutis]

I think that migration to draft 8 can be delivered as a minor fix version, so no changes will be needed

[dzarras]

@babisRoutis Check this diff: https://author-tools.ietf.org/iddiff?url1=draft-ietf-oauth-selective-disclosure-jwt-07&url2=draft-ietf-oauth-selective-disclosure-jwt-08&difftype=--html

In draft8, enveloped SD-JWTs (draft7 Section 10) seems to have been removed.

[babisRoutis]

@babisRoutis Check this diff: https://author-tools.ietf.org/iddiff?url1=draft-ietf-oauth-selective-disclosure-jwt-07&url2=draft-ietf-oauth-selective-disclosure-jwt-08&difftype=--html

In draft8, enveloped SD-JWTs (draft7 Section 10) seems to have been removed.

Good catch Dimitri. Somehow I totally missed that