mesh-issues: take every condition key the controller raises, a delivery's with its slash among them (hq issue 475)

The tracker's own pattern refused the slash a delivery's id carries, so no issue
could track a delivery's condition and the operator's alert kept saying no issue
tracks it. Mirror the controller's key rule instead of a pattern of our own; a
router test proves a slashed key is matched and named end to end.

modules/messenger/cmd/messenger/tracking_delivery_test.go

@@ -0,0 +1,42 @@
+package main
+
+import (
+	"encoding/json"
+	"strings"
+	"testing"
+)
+
+// A delivery's condition, whose key holds its repository as owner/name, is matched to the issue that tracks it and
+// its message names that issue (novox/hq issue 475). The key is the real one `mesh-controller.status` named; the
+// event is decoded as the controller says it, so the key travels as it does on the bus.
+func TestADeliverysConditionWithASlashInItsKeyNamesTheIssueThatTracksIt(t *testing.T) {
+	const key = "delivery.novox/mesh-controller_d2e9dc61590f.stalled"
+	h, tg, _, c, _ := newHolder(t)
+	h.Ask = func(address string, body any) (json.RawMessage, error) {
+		if address != TrackingVerb {
+			return json.RawMessage(`{"ok":true}`), nil
+		}
+		return json.RawMessage(`{"conditions":{"` + key + `":[{"number":475,"status":"open"}]}}`), nil
+	}
+	k, err := DecodeCondition(EventRaised, []byte(`{"key":"`+key+`","kind":"stalled","severity":"urgent",`+
+		`"subject":{"scope":"delivery","id":"novox/mesh-controller_d2e9dc61590f"},`+
+		`"headline":"Delivery of mesh-controller stalled",`+
+		`"explanation":"Needs you: let the walk go or drop it. The delivery of mesh-controller waits for a walk that never starts.",`+
+		`"needs":"let the walk go or drop it.","summary":"the delivery of mesh-controller waits for its walk"}`))
+	if err != nil {
+		t.Fatal(err)
+	}
+	if k.Key != key {
+		t.Fatalf("the key was read as %q", k.Key)
+	}
+	k.Raised = c.now()
+	h.Condition(EventRaised, k)
+	settle(h, c)
+	if len(tg.sends) != 1 {
+		t.Fatalf("telegram %d", len(tg.sends))
+	}
+	body := tg.sends[0].Body
+	if !strings.Contains(body, "Tracked as issue 475") || strings.Contains(body, "No issue tracks this yet.") {
+		t.Fatalf("body: %q", body)
+	}
+}