Found by fixing 027 and pushing again. The declaration is now accepted
and the database container still cannot start: the mesh's own store
holds 5432 on that machine, and the module publishes 5432.
Nothing catches it because the substrate is not a module. It arrives
from the bundle before there is a mesh to ask, so the control plane has
never heard of the store and does not know it holds a port. Resolution
can compare modules with each other and cannot compare one against what
the mesh is built on.
Nor does it compare modules with each other. A port is exclusive on a
machine in exactly the way a claim is, and the mesh has a mechanism for
that which ports do not use.
It has been met before: the end-to-end test that exercises a real
database publishes 5433 rather than 5432, inline, with nothing saying
why. That is how a constraint becomes folklore.
The open question is bigger than the bug. Whether a module should
publish to the machine at all decides how a consumer reaches it, and
changes what `serves` means.
jschoubben
6330abce5f