Read the foundation's ports from each node's settings, wherever a port is used (hq ADR 0100)

internal/inventory/ports_test.go

@@ -236,3 +236,24 @@ func TestUnassigningReleasesTheModulesPorts(t *testing.T) {
 		t.Fatalf("port 25 is still held in the name of a module that was unassigned: %v", err)
 	}
 }
+
+// novox/hq ADR 0100: a port a node was given for a module is the node's, and the mesh never hands
+// it to another.
+func TestAGivenPortIsNeverAssigned(t *testing.T) {
+	inv, node := aNodeWithModules(t, "postgres", "web")
+	ctx := t.Context()
+	if err := inv.SetSettings(ctx, node, "postgres",
+		map[string]any{catalogue.PortsSetting: map[string]any{"5432": 20000}}); err != nil {
+		t.Fatal(err)
+	}
+	got, err := inv.PortFor(ctx, node, "web", 8080, false)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if got.Machine == 20000 {
+		t.Fatal("a port given to postgres was assigned to web")
+	}
+	if _, err := inv.PortFor(ctx, node, "web", 20000, true); !errors.Is(err, ErrPortTaken) {
+		t.Fatalf("a fixed port given to another module was handed over: %v", err)
+	}
+}