Policy chain revocation architecture

[anvabr]

Problem description

#2075 introduced the capability of linking independently executed policies (or modules) into a chain, the execution of each link in such chains can be automatically triggered by the previous link via publishing a document of the type which has been configured to be the 'source' for the link.

However revocation events are currently not handled properly across chain links, which causes issues for trust chain in the case where some documents are invalidated upstream.

Requirements

Implement the revocation flow which supports policy chains such that a revocation of the document 'upstream' was handled correctly in all 'downstream' chain links as if this was a single policy/instances.

Definition of done

• Revocation cascading flow supports cross-links dependencies in Policy chains
• Trust chain (Policy chain trust chain discovery and display #2236) supports policy chain revocation by correctly identifying and displaying the status of revoked documents
• All revocation events are recorded in Hedera topics such that external tools are able to use it
• Documentation is updated accordingly

Acceptance criteria

• Revocation works in the same way regardless whether the token/document was produced as a result of the execution of a single Policy instance or a policy chain.