morph: add method for container's members updates

Follows nspcc-dev/neofs-contract#438.

Signed-off-by: Pavel Karpy <carpawell@nspcc.ru>

pkg/morph/client/container/client.go

@@ -39,6 +39,9 @@ const (
 
 	// putNamedMethod is method name for container put with an alias. It is exported to provide custom fee.
 	putNamedMethod = "putNamed"
+
+	addNextEpochNodes         = "addNextEpochNodes"
+	commitContainerListUpdate = "commitContainerListUpdate"
 )
 
 var (

pkg/morph/client/container/nodes.go

@@ -0,0 +1,50 @@
+package container
+
+import (
+	"fmt"
+
+	"github.com/nspcc-dev/neofs-node/pkg/morph/client"
+)
+
+// AddNextEpochNodes registers public keys as a container's placement vector
+// with specified index. Registration must be finished with final
+// [Client.CommitContainerListUpdate] call. Always sends a notary request with
+// Alphabet multi-signature.
+func (c *Client) AddNextEpochNodes(cid []byte, placementIndex int, nodesKeys [][]byte) error {
+	if len(cid) == 0 || len(nodesKeys) == 0 {
+		return errNilArgument
+	}
+
+	prm := client.InvokePrm{}
+	prm.SetMethod(addNextEpochNodes)
+	prm.SetArgs(cid, placementIndex, nodesKeys)
+	prm.RequireAlphabetSignature()
+
+	err := c.client.Invoke(prm)
+	if err != nil {
+		return fmt.Errorf("could not invoke method (%s): %w", addNextEpochNodes, err)
+	}
+
+	return nil
+}
+
+// CommitContainerListUpdate finishes container placement updates for the current
+// epoch made by former [Client.AddNextEpochNodes] calls. Always sends a notary
+// request with Alphabet multi-signature.
+func (c *Client) CommitContainerListUpdate(cid []byte, replicas []uint32) error {
+	if len(cid) == 0 || len(replicas) == 0 {
+		return errNilArgument
+	}
+
+	prm := client.InvokePrm{}
+	prm.SetMethod(commitContainerListUpdate)
+	prm.SetArgs(cid, replicas)
+	prm.RequireAlphabetSignature()
+
+	err := c.client.Invoke(prm)
+	if err != nil {
+		return fmt.Errorf("could not invoke method (%s): %w", commitContainerListUpdate, err)
+	}
+
+	return nil
+}