Let a module declare a stream of its own and restrict who hears it by a trusted config value (hq issue 718, ADR 0363)

mesh-mail's events must live on a stream of their own and reach only the modules the operator granted
an account (ADR 0359 §2, §4). The controller now creates a module's declared stream, publishes its events
on mesh.stream.<module>.event.<event>, and composes a consumer's durable consumer, filters and bus grants
on a restricted stream only where its consumes asks and the provider's trusted value names it; a consumer
that loses its grant has its consumer removed on the next assertion. Nothing changes while no manifest
declares a stream.

cmd/mesh-controller/busobjects.go

@@ -60,9 +60,19 @@ func assertBusObjects(ctx context.Context, inv *inventory.Inventory, r broker.Ra
 	if err != nil {
 		return nil, err
 	}
+	// And every module's own stream (novox/hq ADR 0363), from the catalogue, before the consumers on it.
+	modStreams, err := inv.DeclaredStreams(ctx)
+	if err != nil {
+		return nil, err
+	}
 	// Every one tried, and every failure named: one module's consumer the bus refuses is no reason
 	// the modules after it in the list hear nothing (novox/hq issue 208, where this runs on each send).
 	var failed []error
+	for _, s := range broker.ModuleStreams(modStreams) {
+		if err := r.EnsureStream(s); err != nil {
+			failed = append(failed, fmt.Errorf("the module stream %s: %w", s.Name, err))
+		}
+	}
 	for _, s := range trafficStreams {
 		if err := r.EnsureStream(s); err != nil {
 			failed = append(failed, fmt.Errorf("the work queue %s: %w", s.Name, err))
@@ -78,6 +88,21 @@ func assertBusObjects(ctx context.Context, inv *inventory.Inventory, r broker.Ra
 			failed = append(failed, fmt.Errorf("how %s on %s hears what it consumes: %w", c.Module, c.Node, err))
 		}
 	}
+	// **And a consumer no longer granted loses what it reads through** (novox/hq ADR 0363 §6): every consumer
+	// on a module's stream the composition no longer asks for is removed, on this very send.
+	if p, prunes := r.(broker.Pruner); prunes && len(modStreams) > 0 {
+		var wanted []broker.Consumer
+		for _, c := range consumers {
+			wanted = append(wanted, c.Consumer)
+		}
+		removed, err := broker.PruneHeard(p, modStreams, wanted)
+		if err != nil {
+			failed = append(failed, err)
+		}
+		for _, gone := range removed {
+			fmt.Printf("  removed the consumer %s: its module is no longer granted that stream (novox/hq ADR 0363)\n", gone)
+		}
+	}
 	if len(failed) > 0 {
 		return nil, errors.Join(failed...)
 	}