[#1324] services/tree: Implement Object Tree Service

Object Tree Service allows changing trees assotiated with
the container in runtime.

Signed-off-by: Evgenii Stratonikov <evgeniy@nspcc.ru>

pkg/services/tree/options.go

@@ -0,0 +1,59 @@
+package tree
+
+import (
+	"crypto/ecdsa"
+
+	"github.com/nspcc-dev/neofs-node/pkg/core/container"
+	"github.com/nspcc-dev/neofs-node/pkg/core/netmap"
+	"github.com/nspcc-dev/neofs-node/pkg/local_object_storage/pilorama"
+	"go.uber.org/zap"
+)
+
+type cfg struct {
+	log       *zap.Logger
+	key       *ecdsa.PrivateKey
+	nmSource  netmap.Source
+	cnrSource container.Source
+	forest    pilorama.Forest
+}
+
+// Option represents configuration option for a tree service.
+type Option func(*cfg)
+
+// WithContainerSource sets a container source for a tree service.
+// This option is required.
+func WithContainerSource(src container.Source) Option {
+	return func(c *cfg) {
+		c.cnrSource = src
+	}
+}
+
+// WithNetmapSource sets a netmap source for a tree service.
+// This option is required.
+func WithNetmapSource(src netmap.Source) Option {
+	return func(c *cfg) {
+		c.nmSource = src
+	}
+}
+
+// WithPrivateKey sets a netmap source for a tree service.
+// This option is required.
+func WithPrivateKey(key *ecdsa.PrivateKey) Option {
+	return func(c *cfg) {
+		c.key = key
+	}
+}
+
+// WithLogger sets logger for a tree service.
+func WithLogger(log *zap.Logger) Option {
+	return func(c *cfg) {
+		c.log = log
+	}
+}
+
+// WithStorage sets tree storage for a service.
+func WithStorage(s pilorama.Forest) Option {
+	return func(c *cfg) {
+		c.forest = s
+	}
+}