`at` was settable. A node setting could point the builder's package binding at
any host, and the builder sends its registry credential there as basic auth — so
a setting meant for a port was a way to hand the password to somebody else.
novox/hq 04-ISSUES/085
The forge is raised by hand at genesis, before any module provides
`package-registry`, so the builder carries a binding instead of resolving one —
and the port in it was rewritten, as text, by the installer. A later
registration of this manifest from the catalogue put 3000 back, silently, and
pointed the builder and its registry credential at whatever holds that port.
Made settable instead: the port is a per-node setting the controller holds, and
the catalogue's number is only its default. `provision`, `from` and `as` are
protected — a setting here is about where the forge answers, never about who the
binding is with.
novox/hq 04-ISSUES/085, ADR 0100
jschoubben