SOLIDUI: allow linking a new pod to webid in profile settings

[jesscmoore]

Description

This is the solidui component of work to allow a user to link another pod to their webid. See also related issue in solidpod

Support editing of a user's webid to link that webid to a new Pod Solid server, by allowing the user to add a RDF triple with

1. oidcIssuerRegistrationToken provided by new Pod SOlid server during the browser based linkage process to validate that the webid belongs to the user

And the new Pod Solid server as an oidcIssuer
2. oidcIssuer

Then allow the user to remove the temporary oidcIssuerRegistrationToken from their webid

Why

As a user I may want Pods on multiple different Solid servers, linked to the same webid on one particular Solid server.

Closing Criteria

Checklist for closing the issue:

• No errors from make prep
• All tests pass make qtest
• User can add these RDF triples to their webid, as shown by checking the webid in a browser.

Alternatives

Editing one's webid can also be done with the Penny app https://penny.vincenttunru.com/

Additional Context

[jesscmoore]

Approach being trialed, is a dialog within Profile Settings, allowing user to link another Pod to their webid.

The alternative is fully automated via CSS Account API by editing solidpod's css_account_api.dart to manage linking an existing webid during creating a pod via a Solid app. Both options are probably useful.

Claude:

A few real alternatives exist at different points in the design:

1. How verification completes (the biggest fork):

Manual (current plan): user adds the token via our dialog, then leaves the app to click "Link WebID" again on the other Pod's own website to verify, then comes back to click "Finish Linking". Works with any Solid server, no extra credentials needed in-app.
Fully automated via CSS Account API: extend solidpod's existing css_account_api.dart (which already logs into a CSS account and drives its JSON API for password changes/account creation) with a function that also logs into the target Pod's account (email+password), requests the link, writes the token triple, and immediately calls CSS's verify step itself — no browser round-trip at all. Only works on CSS servers (not NSS/ESS), and requires asking the user for the target account's email+password in our dialog rather than just a token.
2. How the WebID document is edited:

Targeted SPARQL PATCH (current plan): updateFileByQuery inserts/deletes just the one triple, leaving everything else in the document untouched — matches the pattern already used elsewhere in solidpod.
Full read-modify-write: fetch the whole document, parse it with turtleToTripleMap, mutate, re-serialize with tripleMapToTurtle, and PUT the whole thing back — same pattern as the existing avatar/display-name code, but riskier since round-tripping through rdflib could reformat or drop triples it doesn't fully understand.
3. Where the UI lives:

Inside the existing Settings dialog (current plan): matches what you described, minimal new surface area.
A dedicated full-screen "Manage WebID" page: more room to show a long turtle document and multiple linked issuers, but a bigger UI addition.
My recommendation is to keep the current plan (manual verification, targeted PATCH, inside Settings) — it's the smallest, most portable change. Option 1's automated variant is the one worth seriously considering as a bigger follow-up since it removes a clunky manual step entirely.

[jesscmoore]

Claude plan:

Add a "Link another Pod" WebID editor to the Settings dialog

Solidui apps sign users in against their WebID's own Pod server. To let a user also register their existing WebID as a login for a second Community Solid Server (e.g. linking https://pods.solidcommunity.au/jessicamoore/profile/card#me to a new account on https://pods.privateinsights.au), CSS's own account webpage requires proof of WebID ownership: the user must add an RDF triple

<webid> <http://www.w3.org/ns/solid/terms#oidcIssuerRegistrationToken> "<token>" 

to their WebID document, then click "Link WebID to account" again on that Pod's webpage to verify.

Once verified, the token triple should be removed and replaced with

<webid> <http://www.w3.org/ns/solid/terms#oidcIssuer> <https://pods.privateinsights.au> 

so Solid-OIDC-aware apps can discover that issuer from the WebID in future.

There is currently no way to edit these triples from within a Solidui app — users would have to hand-edit their WebID document out of band. This plan adds that capability to the existing Settings dialog (SolidProfileEditor, opened from the profile avatar's popup menu in solid_scaffold_appbar_builder.dart), since the user is already authenticated to the Pod that hosts their own WebID at that point, so the existing OIDC/DPoP session can be used to PATCH it.

Confirmed design (per user):

The WebID section is read-only display of the fetched turtle — all mutation happens through guided buttons, not free text editing.

Linking is a guided 2-stage dialog: stage 1 collects the target Pod URL
registration token and adds the token triple; stage 2 ("Finish Linking") removes the token triple and adds solid:oidcIssuer for that Pod URL. Reopening the dialog later re-detects a pending token already present in the fetched turtle and jumps straight to stage 2, re-asking only for the Pod URL (the token value itself is never re-asked for).

[jesscmoore]

This assumes the user is creating their new Pod on server 2 from the web browser pointed to
https:[pods.server2], and has added email login and password for the new Pod account

They then click 'Create pod', enter a pod name, and elect to 'Use an external WebID' which they point to their pods.solidcommunity.au webid, and click 'Create pod'

The browser shows the info about their new pod

On 'back' click

They elect to then click 'Link WebID' and in the choose webid page, add their pods.solidcommunity.au webid, and click 'Link WebID to account'

To demonstrate their own that webid, it asks them to add an oidcRegistrationToken temporarily to their pods.solidcommunity.au webid. They do this by logging into any solid app, eg notepod with their pods.solidcommunity.au webid, in profile settings, click 'Link another Pod' and enter the oidcregistrationtoken and server name of server 2.

After finishing linking, their pods.solidcommunity.au webid is:

And pods.[server2] login page looks like