LookoutUI: configure displayname

[d2burkhalter]

What type of PR is this?

This PR allows operators to configure which oidc claim is used to display a username

What this PR does / why we need it

Currently the username is set to the sub claim which is not always human readable for example when doing local development using authentication with Keycloak
Default:

With uiConfig.oidc.displayNameClaim=name:

Special notes for your reviewer

[greptile-apps]

Greptile Summary

This PR adds a configurable displayNameClaim field to the OIDC configuration, letting operators specify which OIDC claim (e.g. name, preferred_username, email) is shown as the username in Lookout UI instead of always defaulting to sub. The change is consistent across the Go config struct (OidcConfig.DisplayNameClaim *string) and the TypeScript interface (displayNameClaim?: string), and a worked example for local Keycloak development is included in _local/lookout/config-auth.yaml.

Key points:

• The Go side correctly uses omitempty so the field is absent from the JSON payload when not configured, and the TS side marks the field optional — the two sides are symmetric.
• The named OidcConfig struct is a welcome refactor over the previous anonymous struct, making future extensions cleaner.
• The hook correctly guards the claim value with typeof displayName === "string" before using it, and emits a console.warn (with a useful message) when the configured claim is absent or wrong-typed — addressing the silent-fallback concern from a prior review.
• getConfig() is called at module level rather than inside the hook; this works fine for a static SPA config but couples the hook to module-initialization order and can complicate unit tests that swap configs between cases (see inline comment).

Confidence Score: 4/5

• PR is safe to merge; the one inline suggestion is non-blocking and only affects testability.
• The implementation is correct end-to-end — Go struct, TypeScript interface, and hook logic are all consistent. Previous review concerns (silent fallback, type width) have been fully addressed with a console.warn and a plain string type. The only remaining note is the module-level getConfig() call, which is a style/testability concern rather than a runtime bug.
• No files require special attention; hooks.ts has a minor testability note about the module-level getConfig() call.

Important Files Changed

Filename	Overview
internal/lookoutui/src/oidcAuth/hooks.ts	Adds displayNameClaim resolution logic with proper string-type guard and console.warn fallback; config is read at module level rather than inside the hook, which is safe for a static SPA config but worth noting.
internal/lookout/configuration/types.go	Extracts anonymous Oidc struct into a named OidcConfig type and adds DisplayNameClaim *string with appropriate omitempty tagging and doc comment.
internal/lookoutui/src/config/types.ts	Adds optional displayNameClaim?: string to OidcConfig interface, matching the Go side's *string (omitempty) — correct and consistent.
_local/lookout/config-auth.yaml	Adds displayNameClaim: "name" example for local Keycloak development; comment is clear and accurate.

Sequence Diagram

sequenceDiagram
    participant Server as Go Server
    participant Window as window.__LOOKOUT_UI_CONFIG__
    participant Config as getConfig()
    participant Hook as useUsername hook
    participant OIDC as OIDC UserManager
    participant UI as React UI

    Server->>Window: Serve UIConfig (with oidc.displayNameClaim)
    Note over Config: Module initialization (once)
    Window->>Config: getConfig() reads config
    Config-->>Hook: config (module-level constant)

    Hook->>OIDC: userManager.getUser()
    OIDC-->>Hook: user (with profile claims)

    alt displayNameClaim configured
        Hook->>Hook: profile[displayNameClaim]
        alt claim is a string
            Hook->>UI: setUsername(displayName)
        else claim missing or not a string
            Hook->>Hook: console.warn(misconfiguration)
            Hook->>UI: setUsername(user.profile.sub)
        end
    else no displayNameClaim
        Hook->>UI: setUsername(user.profile.sub)
    end

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_{Reviews (2): Last reviewed commit: "fix: make displayNameClaim type more gen..." | Re-trigger Greptile}