[#64] object: move package from neofs-api-go

Also, remove deprecated method.

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

object/object.go

@@ -0,0 +1,45 @@
+package object
+
+import (
+	"github.com/nspcc-dev/neofs-api-go/v2/object"
+)
+
+// Object represents v2-compatible NeoFS object that provides
+// a convenient interface for working in isolation
+// from the internal structure of an object.
+//
+// Object allows to work with the object in read-only
+// mode as a reflection of the immutability of objects
+// in the system.
+type Object struct {
+	*rwObject
+}
+
+// NewFromV2 wraps v2 Object message to Object.
+func NewFromV2(oV2 *object.Object) *Object {
+	return &Object{
+		rwObject: (*rwObject)(oV2),
+	}
+}
+
+// New creates and initializes blank Object.
+//
+// Works similar as NewFromV2(new(Object)).
+func New() *Object {
+	return NewFromV2(new(object.Object))
+}
+
+// ToV2 converts Object to v2 Object message.
+func (o *Object) ToV2() *object.Object {
+	if o != nil {
+		return (*object.Object)(o.rwObject)
+	}
+
+	return nil
+}
+
+// MarshalHeaderJSON marshals object's header
+// into JSON format.
+func (o *Object) MarshalHeaderJSON() ([]byte, error) {
+	return (*object.Object)(o.rwObject).GetHeader().MarshalJSON()
+}