[#30] add object name resolving

Signed-off-by: Pavel Pogodaev <p.pogodaev@yadro.com>

api/layer/tree_service.go

@@ -0,0 +1,22 @@
+package layer
+
+import (
+	"context"
+	"errors"
+
+	"git.frostfs.info/TrueCloudLab/frostfs-http-gw/api"
+	cid "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/container/id"
+)
+
+// TreeService provide interface to interact with tree service using s3 data models.
+type TreeService interface {
+	GetLatestVersion(ctx context.Context, cnrID *cid.ID, objectName string) (*api.NodeVersion, error)
+}
+
+var (
+	// ErrNodeNotFound is returned from Tree service in case of not found error.
+	ErrNodeNotFound = errors.New("not found")
+
+	// ErrNodeAccessDenied is returned from Tree service in case of access denied error.
+	ErrNodeAccessDenied = errors.New("access denied")
+)

api/tree.go

@@ -0,0 +1,17 @@
+package api
+
+import (
+	oid "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/object/id"
+)
+
+// NodeVersion represent node from tree service.
+type NodeVersion struct {
+	BaseNodeVersion
+	DeleteMarker bool
+}
+
+// BaseNodeVersion is minimal node info from tree service.
+// Basically used for "system" object.
+type BaseNodeVersion struct {
+	OID oid.ID
+}