Firefox doesn't send If-None-Match header in subsequent requests for Entity List

[lognaturel]

Problem description

Entity Lists are never returned from Firefox cache because theIf-None-Match header is never sent. Other resources (formList, manifest, static file attachment) use the If-None-Match header and browser cache as expected.

Steps to reproduce the problem

1. Create a form with an Entity List, populate some Entities
2. Open the browser inspection tool
3. Download that Entity List from the data table page (e.g. https://test.getodk.cloud/#/projects/523/entity-lists/trees/entities), see a 200 response
4. Download it again and see a 200 response again. Notice the If-None-Match header is not sent

Expected behavior

The If-None-Match header is used and subsequent requests get 304 responses.

Central version shown in version.txt

versions:
801ab503c74eaa24b27a226622eceee9351d5db0 (v2024.2.1-10-g801ab50)
+5e95312bc6177ed79f170d8851da39fe327219d4 client (v2024.2.1-63-g5e95312b)
+4355d9e4c3a0f7bb6b694aad4cf318145905da2e server (v2024.2.0-114-g4355d9e4)

Browser version

Firefox 132.0.2 (aarch64)

Other notes (if any)

I am stumped! See #662 (comment) for headers for Entity Lists vs. static files.