Improve Headers For Browser Caching

[thehabes]

Supports CenterForDigitalHumanities/glossing-entries#323.

Problem

GET /gog/id/:_id returns an entity with its targeting Annotations merged in, but sets Last-Modified from match — the raw document from findOne, captured before expand() runs:

let match = await db.findOne({ ... })          // line 433
...
res.set(utils.configureLastModifiedHeader(match))   // line 441
res.set("Current-Overwritten-Version", ...)
let expanded = await expand(match)             // line 446

configureLastModifiedHeader (utils.js:222-241) derives the date from __rerum.isOverwritten or __rerum.createdAt. Both describe the root entity only. The merged Annotations are never in scope for that header.

The result is a header that does not move when a targeting Annotation is added, changed, or removed — a wrong freshness signal for the composed body. Confirmed empirically: adding an Annotation changed the body and the ETag, and left Last-Modified untouched.

Related

Pairs with CenterForDigitalHumanities/glossing-entries#324, which stops the GoG client reading form-prefill data through the browser cache. Neither PR depends on the other; this one removes a latent trap for future clients and intermediaries.