Resolving references from public share

[mejo-]

Is your feature request related to a problem? Please describe.

Currently references don't get resolved in public shares. The reference resolve endpoint allows only authenticated requests. This results in a broken user experience when browsing public shares, e.g. when text documents or collectives pages contain link previews.

Describe the solution you'd like

The idea is to add new PublicPage endpoints to the ReferenceApiController that lookup ReferenceProviders which explicitly support public lookups. It's necessary to separate public from authenticated lookups as many providers look up data that is only accessible to authenticated users.

I'm not exactly sure yet how the implementation details could look like. One idea:

1. Add a new interface IReferenceProviderPublic with functions matchReferencePublic() and resolveReferencePublic()
2. In ReferenceApiController define new endpoints like GET /references/resolvePublic that call $this-referenceManager->resolveReference() with $public = true.
3. In ReferenceManager only regard providers that implement IReferenceProviderPublic for public lookups (with $public = true).
4. The default LinkReferenceProvider should just do the same for public and authenticated lookups as it only does opengraph anyway.
5. Custom reference providers (e.g. the Collectives one) can implement custom resolveReferencePublic() functions for a public share of a collective.

In the frontend, NcReferenceList would call either the public or the authenticated reference API endpoints depending on whether it's an authenticated user session or not.

Open questions

In order to lookup a page in a collective share, resolveReferencePublic() would need to get the share token of the current collective. Not sure yet how best to pass it there. resolveReferencePublic() could get sourceUrl as second parameter.

[mejo-]

I opened PRs against server and nextcloud-vue that implement a first version of this:

• feat(Reference): Add public API endpoints to get references #46378
• feat(NcRichText): Call public reference API when unauthenticated nextcloud-libraries/nextcloud-vue#5800

Feedback welcome (@juliushaertl, @julien-nc, @max-nextcloud)

[mejo-]

This is fixed with #46378 and nextcloud-libraries/nextcloud-vue#5800 being merged.