An address is read from the node's settings where it is used, never recorded with a port

Three readers did not follow a moved foundation port (novox/hq 04-ISSUES/102),
and each took the control-node down in its own way: the control plane's own
store and broker connections, sealed at genesis with the port inside; and every
build the mesh ever recorded, kept as `<registry>:<port>/<module>/<artifact>@…`.

The control plane cannot open its own sealed connections to move a port, and it
cannot bind the store as a consumer would — a binding mints a credential. So its
settings get a third twin: `NAME_PORT`, composed into its container from the
node's settings by a placeholder that names a seat, `${seat:mesh-store:5432}`,
and read on top of the sealed value by the store, the broker, the management API
and the bus connection. The answer is empty when the mesh has nothing to add,
so what genesis wrote stands until the node says otherwise.

A build is now recorded by digest and path — `artifact-store://<module>/<artifact>@…`
— and the store's address is composed in where a reference is used: the
declaration, the trust file, the bases a build is handed, a replay to the
catalogue. A reference recorded before this, with an address, is re-routed the
same way when the mesh built it. The trust file and every provider's address
now come from one derivation, with the node's given port over the mesh's
assignment over the manifest's number.

novox/hq 04-ISSUES/102

internal/broker/broker.go

@@ -40,8 +40,12 @@ type Broker struct {
 var ErrNotConfigured = errors.New("this control plane has not been told about its broker")
 
 // FromEnvironment reads the two settings, if they are there.
+//
+// The address's port follows MESH_BROKER_ADDRESS_PORT when the node's settings moved the bus
+// (novox/hq 04-ISSUES/102): the address genesis wrote is a public name and the port genesis
+// chose, and only the port is the node's to move.
 func FromEnvironment() (Broker, error) {
-	address, err := envfile.Value(AddressVar)
+	address, err := envfile.Placed(AddressVar)
 	if err != nil {
 		return Broker{}, err
 	}

internal/broker/broker_test.go

@@ -178,3 +178,32 @@ func TestBothTogetherGiveABroker(t *testing.T) {
 		t.Errorf("got %+v", known)
 	}
 }
+
+// The node moved the bus, and the address a token carries follows (novox/hq 04-ISSUES/102).
+func TestTheAddressPortFollowsThePortTwin(t *testing.T) {
+	t.Setenv(AddressVar, "broker.example:5671")
+	t.Setenv(AddressVar+"_FILE", "")
+	path, _ := writeCertificate(t)
+	t.Setenv(CertificateVar, path)
+	t.Setenv(AddressVar+"_PORT", "5679")
+	b, err := FromEnvironment()
+	if err != nil {
+		t.Fatal(err)
+	}
+	if b.Address != "broker.example:5679" {
+		t.Fatalf("the address is %q; the node put the bus on 5679", b.Address)
+	}
+}
+
+func TestTheManagementPortFollowsThePortTwin(t *testing.T) {
+	t.Setenv(ManagementVar, "http://guest:guest@127.0.0.1:15672")
+	t.Setenv(ManagementVar+"_FILE", "")
+	t.Setenv(ManagementVar+"_PORT", "15673")
+	m, err := ManagementFromEnvironment()
+	if err != nil {
+		t.Fatal(err)
+	}
+	if m.base.Host != "127.0.0.1:15673" {
+		t.Fatalf("the management API is at %q; the node put it on 15673", m.base.Host)
+	}
+}

internal/broker/management.go

@@ -41,8 +41,11 @@ type Management struct {
 }
 
 // ManagementFromEnvironment reads where the management API is, if it is configured.
+//
+// On the port MESH_BROKER_MANAGEMENT_PORT names when the node moved it (novox/hq 04-ISSUES/102);
+// the URL's own port otherwise.
 func ManagementFromEnvironment() (*Management, error) {
-	raw, err := envfile.Value(ManagementVar)
+	raw, err := envfile.Placed(ManagementVar)
 	if err != nil {
 		return nil, err
 	}