[#83] pkg/client: Support status returns

Make all `Client` methods to return structured values and error. Parse v2
status messages in all RPC and provide status getter from all result
structures. Returns status failures as status result instead of error.

Interface changes:
  * all methods return `<method>Res` structure;
  * rename some methods to be more clear;
  * unify TZ and SHA256 objecy payload hashing in single method.

Behavior changes:
  * client doesn't verify object header structure received via Object.Head.
    If the caller was tied to verification, now it must do it explicitly.

Signed-off-by: Leonard Lyubich <leonard@nspcc.ru>

client/session.go

@@ -10,18 +10,41 @@ import (
 	v2session "github.com/nspcc-dev/neofs-api-go/v2/session"
 	v2signature "github.com/nspcc-dev/neofs-api-go/v2/signature"
 	"github.com/nspcc-dev/neofs-sdk-go/owner"
-	"github.com/nspcc-dev/neofs-sdk-go/session"
 )
 
 // Session contains session-related methods.
 type Session interface {
 	// CreateSession creates session using provided expiration time.
-	CreateSession(context.Context, uint64, ...CallOption) (*session.Token, error)
+	CreateSession(context.Context, uint64, ...CallOption) (*CreateSessionRes, error)
 }
 
 var errMalformedResponseBody = errors.New("malformed response body")
 
-func (c *clientImpl) CreateSession(ctx context.Context, expiration uint64, opts ...CallOption) (*session.Token, error) {
+type CreateSessionRes struct {
+	statusRes
+
+	id []byte
+
+	sessionKey []byte
+}
+
+func (x *CreateSessionRes) setID(id []byte) {
+	x.id = id
+}
+
+func (x CreateSessionRes) ID() []byte {
+	return x.id
+}
+
+func (x *CreateSessionRes) setSessionKey(key []byte) {
+	x.sessionKey = key
+}
+
+func (x CreateSessionRes) SessionKey() []byte {
+	return x.sessionKey
+}
+
+func (c *clientImpl) CreateSession(ctx context.Context, expiration uint64, opts ...CallOption) (*CreateSessionRes, error) {
 	// apply all available options
 	callOptions := c.defaultCallOptions()
 
@@ -55,25 +78,30 @@ func (c *clientImpl) CreateSession(ctx context.Context, expiration uint64, opts
 		return nil, fmt.Errorf("transport error: %w", err)
 	}
 
-	// handle response meta info
-	if err := c.handleResponseInfoV2(callOptions, resp); err != nil {
-		return nil, err
-	}
+	var (
+		res     = new(CreateSessionRes)
+		procPrm processResponseV2Prm
+		procRes processResponseV2Res
+	)
 
-	err = v2signature.VerifyServiceMessage(resp)
-	if err != nil {
-		return nil, fmt.Errorf("can't verify response message: %w", err)
+	procPrm.callOpts = callOptions
+	procPrm.resp = resp
+
+	procRes.statusRes = res
+
+	// process response in general
+	if c.processResponseV2(&procRes, procPrm) {
+		if procRes.cliErr != nil {
+			return nil, procRes.cliErr
+		}
+
+		return res, nil
 	}
 
 	body := resp.GetBody()
-	if body == nil {
-		return nil, errMalformedResponseBody
-	}
 
-	sessionToken := session.NewToken()
-	sessionToken.SetID(body.GetID())
-	sessionToken.SetSessionKey(body.GetSessionKey())
-	sessionToken.SetOwnerID(ownerID)
+	res.setID(body.GetID())
+	res.setSessionKey(body.GetSessionKey())
 
-	return sessionToken, nil
+	return res, nil
 }