Let a module declare a log the controller creates and never removes (ADR 0297)

The issue tracker's history lasts seven days on the events stream and its
bucket fills toward a cap with no warning (issues 501, 502). A module may
now declare `logs`; the controller creates each as a stream on the bus
(create-or-update, never deleted or recreated, reported when undeclared),
issues it to the owner's assignments in their membership, grants the
runtime exactly the append and direct-read subjects, and raises a
condition when any module's bucket or log reaches 75% of its cap, cleared
below 70%.

internal/broker/jetstream.go

@@ -448,3 +448,41 @@ func (j *JetStream) BucketNames() ([]string, error) {
 	}
 	return out, lister.Error()
 }
+
+// EnsureLog creates a module's log if it is absent and brings its configuration to match if it is
+// present (novox/hq ADR 0297).
+//
+// **An update, never a delete and recreate**, for a bucket's reason: recreating discards what the log
+// holds, and a log is a module's record. A configuration the server will not change in place (its
+// storage, say, on a stream made by hand) is said as this assertion's error and the stream is left as
+// it is — never removed to be made again.
+func (j *JetStream) EnsureLog(l Log) error {
+	js, err := jetstream.New(j.conn)
+	if err != nil {
+		return err
+	}
+	ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
+	defer cancel()
+	if _, err := js.CreateOrUpdateStream(ctx, l.Config()); err != nil {
+		return fmt.Errorf("asserting log %s: %w", l.Stream(), err)
+	}
+	return nil
+}
+
+// LogStreams is every log stream on the server: every stream whose name starts with LogStreamPrefix.
+func (j *JetStream) LogStreams() ([]string, error) {
+	js, err := jetstream.New(j.conn)
+	if err != nil {
+		return nil, err
+	}
+	ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
+	defer cancel()
+	lister := js.StreamNames(ctx)
+	var out []string
+	for name := range lister.Name() {
+		if strings.HasPrefix(name, LogStreamPrefix) {
+			out = append(out, name)
+		}
+	}
+	return out, lister.Err()
+}