Say how a declared bucket and module stream are created, so the grants part makes the same stream the controller does

BucketStreamConfig and ModuleStreamConfig are the stream configurations the controller's
CreateOrUpdateKeyValue (BucketConfig) and StreamConfigFor assert at its start, pure, for the
grants part's create of a bucket or stream a manifest declares and the bus lacks. A log already
has Log.Config. Never used for an update.

Issue: 1790

go/buscompose/create.go

@@ -0,0 +1,88 @@
+package buscompose
+
+import (
+	"time"
+
+	"github.com/nats-io/nats.go/jetstream"
+)
+
+// The streams a manifest declares, as the server is asked to create them (novox/hq ADR 0547 §5, issue 1790): the
+// grants part creates each one the bus does not hold yet, with what the controller asserts at its start, so the two
+// make the same stream. Pure. Only a create is ever asked with these: a stream the bus holds is never updated by the
+// grants part (CreateStreamGrants grants no update).
+
+// BucketStreamConfig is a module's bucket as the stream the controller's CreateOrUpdateKeyValue makes of its options
+// (mesh-controller internal/broker BucketConfig, with no marker age held): the client library's key-value shape
+// (rollup, no delete, direct reads, discard new, a duplicate window of two minutes or the age when shorter) with the
+// mesh's caps, file storage and one replica.
+func BucketStreamConfig(b Bucket) jetstream.StreamConfig {
+	history := b.History
+	if history < 1 {
+		history = 1
+	}
+	age := time.Duration(b.TTLSeconds) * time.Second
+	dupes := 2 * time.Minute
+	if age > 0 && age < dupes {
+		dupes = age
+	}
+	cfg := jetstream.StreamConfig{
+		Name:              "KV_" + b.Bucket(),
+		Description:       b.Why(),
+		Subjects:          []string{"$KV." + b.Bucket() + ".>"},
+		MaxMsgsPerSubject: int64(history),
+		MaxBytes:          StateMaxBytes,
+		MaxAge:            age,
+		MaxMsgSize:        StateMaxValueBytes,
+		Storage:           jetstream.FileStorage,
+		Replicas:          1,
+		AllowRollup:       true,
+		DenyDelete:        true,
+		Duplicates:        dupes,
+		MaxMsgs:           -1,
+		MaxConsumers:      -1,
+		AllowDirect:       true,
+		Discard:           jetstream.DiscardNew,
+	}
+	if b.KeyTTL {
+		cfg.AllowMsgTTL, cfg.SubjectDeleteMarkerTTL = true, KeyTTLMarkerTTL
+	}
+	return cfg
+}
+
+// ModuleStreamConfig is a module's own stream as the controller asserts it (mesh-controller internal/broker
+// StreamConfigFor of ModuleStream.Stream).
+func ModuleStreamConfig(m ModuleStream) jetstream.StreamConfig {
+	s := m.Stream()
+	cfg := jetstream.StreamConfig{
+		Name:              s.Name,
+		Subjects:          s.Subjects,
+		Retention:         jetstream.LimitsPolicy,
+		MaxAge:            time.Duration(s.MaxAge) * time.Second,
+		MaxMsgsPerSubject: int64(s.MaxMsgsPerSubject),
+		Description:       s.Why,
+		AllowDirect:       s.Direct,
+		AllowMsgTTL:       s.AllowMsgTTL,
+	}
+	if s.Retention == RetentionWorkQueue {
+		cfg.Retention = jetstream.WorkQueuePolicy
+	}
+	if s.Restricted || s.WorkQueue {
+		cfg.Metadata = map[string]string{}
+		if s.Restricted {
+			cfg.Metadata[RestrictedMetadata] = "true"
+		}
+		if s.WorkQueue {
+			cfg.Metadata[WorkQueueMetadata] = "true"
+		}
+	}
+	if s.MaxBytes > 0 {
+		cfg.MaxBytes = s.MaxBytes
+	}
+	if s.DiscardNew {
+		cfg.Discard = jetstream.DiscardNew
+	}
+	if s.DuplicatesSeconds > 0 {
+		cfg.Duplicates = time.Duration(s.DuplicatesSeconds) * time.Second
+	}
+	return cfg
+}