FEP-ef61 vocabulary terms

[dahlia]

Background

FEP-ef61 defines vocabulary terms needed for portable ActivityPub objects. Fedify needs these terms in @fedify/vocab before applications can construct and parse portable actor and media objects using generated vocabulary classes.

The main terms needed by FEP-ef61 are:

• gateways, used on portable actors to list the gateway servers where the latest actor document can be retrieved;
• digestMultibase, used on links or media attachments to carry the SHA-256 digest of an external resource.

FEP-ef61 also uses the JSON-LD context https://w3id.org/fep/ef61.

Proposed work

Add the FEP-ef61 vocabulary terms to @fedify/vocab.

The work should include:

• adding the https://w3id.org/fep/ef61 context to the runtime context loader if needed;
• adding a gateways property for actor types;
• adding a digestMultibase property for link and media attachment types where it is needed by the spec;
• choosing generated property names that match Fedify's existing naming conventions;
• running vocabulary code generation;
• updating generated snapshots and exports as needed.

The gateways property should represent an ordered list of HTTP(S) gateway base URIs. FEP-ef61 currently says each gateway item must be an HTTP(S) URI with empty path, query, and fragment components.

The digestMultibase property should be represented as a string value for now. Hashlink parsing and digest verification should be handled in a separate issue.

Scope

This issue is only about adding FEP-ef61 vocabulary terms and generated class support.

It does not include:

• ap:/ap+ef61: URI parsing or canonicalization;
• gateway dereferencing;
• gateway endpoint implementation;
• hashlink parsing or media digest verification;
• Object Integrity Proof policy for portable objects;
• FEP-ae97 client-side signing or registration.

Those should be handled in follow-up issues under #288.

Tests

Add vocabulary regression tests covering parse and serialization behavior.

The tests should cover:

• parsing an actor with a gateways array;
• serializing an actor with gateways;
• preserving gateway order;
• parsing an attachment or link with digestMultibase;
• serializing digestMultibase;
• including or loading the FEP-ef61 context as needed;
• generated class inspection/snapshot updates as required by the vocabulary test suite.

This should be added as a sub-issue of #288.