consider re-adding ecosystem extension examples

[Sakurann]

from #300

Examples text that got removed to merge the PR before 60-day review, later discuss where to put them, if somewhere:

Below are two non-normative examples illustrating how an ecosystem may define the above elements to achieve its specific goals and preferences.

Improved Baseline Interoperability

This ecosystem prioritizes interoperability among all Wallets and Issuers, without requiring any pre-existing relationships, and supports both ISO mdocs and SD-JWT VCs. To achieve this, the ecosystem could define the following:

• Wallets MUST support both mdoc and sd-jwt-vc. Issuers MAY issue in either format.
• Wallets MUST register for the 'haip-vci://' custom scheme, where possible.
• Wallets and Issuers MUST support key attestations in the format specified in Annex D of [@!OIDF.OID4VCI].
• Wallets MUST register for the 'haip-vp://' custom scheme and DC API when they have credentials available, where possible.

Making these choices maximizes interoperability between the parties in the ecosystem while minimizing the burden on Issuers and Verifiers. This comes at the expense of an increased burden on Wallets as well as the potential privacy and security issues in (#interop-key-attestations).

Existing Curve Requirements

This ecosystem places importance on maintaining compatibility with already issued cryptographic curves. To achieve this, the ecosystem could define the following:

• Verifiers MUST support all curves from Cipher Suite 1 as listed in table 22 of (@!ISO.18013-5).
• Verifiers MUST support all hash algorithms in table 21 of (@!ISO.18013-5).
• Issuers MAY sign credentials using any curve from Cipher Suite 1 as listed in table 22 of (@!ISO.18013-5).
• Issuers MAY use any hash algorithm in table 21 of (@!ISO.18013-5).

Making these choices ensures interoperability with any existing Issuer, at the cost of an increased burden on the Verifier.

Originally posted by @Sakurann in #300 (comment)

[Sakurann]

WG discussion:

• agreement that re-adding these is valuable.
• reformat and make it clear that these are just examples, and not exact profiles that implementers need follow.
  • play with MUSTs so that it's clearer
• make sure example profiles cover all bullet points in section 9.3
  • make it clearer whether it is VP or VCI or both that's an example.
  • make bullet points in section 9.3 numbered and map examples to those numbers
• make each example more detailed as much as we can.