feature: add a "profile" for TSM content type

[jraman567]

Problem Description:

We currently use the following two content typed for evidence formats:

• application/vnd.veraison.tsm-report+cbor"
• application/vnd.veraison.configfs-tsm+json

Different attesters (SEV-SNP, TDX, CCA and so on) generate evidence in the same TSM format. Problem arises when we implement different schemes that can accept this evidence format, the top-level handler won't know which scheme to invoke.

Proposed solution

I propose defining a profile to differentiate. Perhaps, we could use the "provider" (sev_guest, tdx_guest and so on) as a string profile ID.

[jraman567]

Discussed this issue in the email.

We thought that the evidence media formats used within Veraison are private (especially the ones under application/vnd) and don't need to be registered with IANA until IETF scrutinizes it. We'll continue to use private media types till then.

Closing as there's nothing to do here. Please re-open if necessary.