Hear a merge's announcement from whichever module claims the delivery seat (issue 1211)

cmd/mesh-controller/moved.go

@@ -5,6 +5,7 @@ import (
 	"encoding/json"
 	"errors"
 	"fmt"
+	"slices"
 	"sort"
 	"strings"
 
@@ -14,6 +15,7 @@ import (
 	"git.novox.be/novox/mesh-sdk/go/asks"
 
 	"github.com/novox/mesh-controller/internal/broker"
+	"github.com/novox/mesh-controller/internal/catalogue"
 	"github.com/novox/mesh-controller/internal/inventory"
 	"github.com/novox/mesh-controller/internal/link"
 )
@@ -115,12 +117,26 @@ func movedOnApprove(d deliveryMerge, ask *asks.Ask, w *asks.Warrant) (string, er
 // keepingDeliveryMerges keeps each merge mesh-delivery announces in the controller's bucket for them.
 type keepingDeliveryMerges struct {
 	js func() *broker.JetStream
+	// catalog is the catalogue, whose modules claiming the delivery seat are the only ones whose word on a merge is
+	// kept (novox/hq ADR 0437 §3).
+	catalog func(ctx context.Context) ([]inventory.Entry, error)
 	// kept, when set, is told each merge once it is kept: a first merge waiting for the word asks its builds then
 	// (novox/hq ADR 0432, issue 1146).
 	kept func(ctx context.Context, d deliveryMerge) error
 }
 
-func (k keepingDeliveryMerges) KeepDeliveryMerge(ctx context.Context, body []byte) error {
+func (k keepingDeliveryMerges) KeepDeliveryMerge(ctx context.Context, emitter string, body []byte) error {
+	if k.catalog == nil {
+		return fmt.Errorf("%w: the catalogue is not read", link.ErrTryAgain)
+	}
+	entries, err := k.catalog(ctx)
+	if err != nil {
+		return fmt.Errorf("%w: %w", link.ErrTryAgain, err)
+	}
+	if !slices.Contains(claimantsOf(entries, catalogue.DeliverySeat), emitter) {
+		return fmt.Errorf("%w: %q is not among %v", link.ErrNotTheDeliverysWord, emitter,
+			claimantsOf(entries, catalogue.DeliverySeat))
+	}
 	d, err := parseDeliveryMerge(body)
 	if err != nil {
 		return err