DAC: Document post-sale data addition

Impacted Sections

List UNTP specification page(s) that are impacted by this issue. For example:

• https://untp.unece.org/docs/specification/DecentralisedAccessContro

Issue Description

Post-sale data addition (repairs, ownership transfers) is a key use case with only conceptual guidance. Concrete workflow documentation enables implementation.

Document complete flow for authorized third parties (e.g. repair facilities) to add events:

1. Authorization grant: Product owner or manufacturer issues authorization credential
2. Authentication: Third party presents authorization credential to Identity Resolver
3. Event creation: Third party creates signed Digital Traceability Event
4. Event linkage: Event linked to product via Identity Resolver linkset
5. Verification: Any verifier can confirm authorization chain

Include:

• Sequence diagram (Mermaid format)
• Sample authorization credential structure
• Link type vocabulary for authorization credentials
• Error cases and recovery procedures

I Have

• Added the relevant labels (e.g. WG-Adoption, WG-Conformity, WG-SupplyChain, WG-Technical, WG-Steering, etc.).