New user/issuer task - Offer Claim

[RieksJ]

Requirement: It MUST be possible for issuers to publish what we here call a 'claim offer', which is a piece of information that not only states (the syntax and semantics of) the claim itself, but also additional information that verifiers may need to determine whether or not they want to request for such claims for a particular purpose.

Motivations: Verifiers need (the contents of) claims so that they can use/process them for a particular purpose and/or to make decisions (such as whether or not to enroll someone in a course). To do that, they need to be able to construct presentation requests (or similar), in which they request the holder to present claims of specific types that are issued by particular issuers. In order to be able to construct such requests, it MUST be possible for the verifier to (a) learn which (kinds of) claims are being issued by which issuers, and (b) determine whether or not (the contents of) such a claim is valid for processing as the verifier intends (where 'valid' means that if the result of such processing is incorrect, or comes with a risk for the verifier that it finds unacceptable, that is not because of (the contents of) that claim.