The drift guard asserts that the full, envelope and legacy paths produce the
same PeerConfig for a fixture. The new destination field was invisible to it:
the frozen legacy implementation never emitted it, so a fixture with a non-empty
account URL would have made legacy disagree with the other two, and no fixture
set one, so nothing failed and the field had no coverage at all.
The legacy path now emits the account setting, which is what AddressV6 already
does. It does not take the deployment-wide default the live path falls back to,
because the harness runs that path with no server config, so the two agree on
every fixture.
The dns-config case pins an account-level URL. Removing the legacy line makes it
fail on the legacy mode for that exact field, which is what makes the fixture
worth having.
riccardom
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