Sign-out: a logout to each marked URL carries the one stored Basic Auth credential #1971

What happens

Studio stores one Basic Auth credential per entity (a cluster or instance), not per URL. A sign-in marker records the URL signed into, and an entity can end up marked at more than one URL, for example after its domain changes. When a sign-out logs out each URL an entity is marked at (#1969), every one of those logout requests carries that single stored credential, including to a URL it was never used with.

Why it's small

The URLs belong to the same entity, and the request is a logout. But a credential going to a host it wasn't entered for is worth closing.

Fix direction

Either store the credential with the URL it was entered for and send it only there, or send the logout with the credential only to the URL the credential was saved for, and without it to the others.

Review-Deferral: face1e3da4c920f7 severity=nit category=security

Raised by the cross-model review of #1969 (#1968). Pre-existing; not introduced there.

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