[#53] session: move XHeader from neofs-api-go

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

session/xheader.go

@@ -0,0 +1,55 @@
+package session
+
+import (
+	"github.com/nspcc-dev/neofs-api-go/v2/session"
+)
+
+// XHeader represents v2-compatible XHeader.
+type XHeader session.XHeader
+
+// NewXHeaderFromV2 wraps v2 XHeader message to XHeader.
+//
+// Nil session.XHeader converts to nil.
+func NewXHeaderFromV2(v *session.XHeader) *XHeader {
+	return (*XHeader)(v)
+}
+
+// NewXHeader creates, initializes and returns blank XHeader instance.
+//
+// Defaults:
+//  - key: "";
+//  - value: "".
+func NewXHeader() *XHeader {
+	return NewXHeaderFromV2(new(session.XHeader))
+}
+
+// ToV2 converts XHeader to v2 XHeader message.
+//
+// Nil XHeader converts to nil.
+func (x *XHeader) ToV2() *session.XHeader {
+	return (*session.XHeader)(x)
+}
+
+// Key returns key to X-Header.
+func (x *XHeader) Key() string {
+	return (*session.XHeader)(x).
+		GetKey()
+}
+
+// SetKey sets key to X-Header.
+func (x *XHeader) SetKey(k string) {
+	(*session.XHeader)(x).
+		SetKey(k)
+}
+
+// Value returns value of X-Header.
+func (x *XHeader) Value() string {
+	return (*session.XHeader)(x).
+		GetValue()
+}
+
+// SetValue sets value of X-Header.
+func (x *XHeader) SetValue(k string) {
+	(*session.XHeader)(x).
+		SetValue(k)
+}