[#979] adm: Add subnet-related commands

Add `subnet` command which contains all subnet-related commands. Add
sub-commands:
  * `create` for creation;
  * `remove` for removal;
  * `get` for reading;
  * `admin` for admin management;
  * `client` for client management.

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

pkg/morph/client/subnet/admin.go

@@ -0,0 +1,87 @@
+package morphsubnet
+
+import "github.com/nspcc-dev/neofs-node/pkg/morph/client"
+
+// ManageAdminsPrm groups parameters of administer methods of Subnet contract.
+//
+// Zero value adds node admin. Subnet, key and group must be specified via setters.
+type ManageAdminsPrm struct {
+	// remove or add admin
+	rm bool
+
+	// client or node admin
+	client bool
+
+	subnet []byte
+
+	admin []byte
+
+	group []byte
+}
+
+// SetRemove marks admin to be removed. By default, admin is added.
+func (x *ManageAdminsPrm) SetRemove() {
+	x.rm = true
+}
+
+// SetClient switches to client admin. By default, node admin is modified.
+func (x *ManageAdminsPrm) SetClient() {
+	x.client = true
+}
+
+// SetSubnet sets identifier of the subnet in a binary NeoFS API protocol format.
+func (x *ManageAdminsPrm) SetSubnet(id []byte) {
+	x.subnet = id
+}
+
+// SetAdmin sets admin's public key in a binary format.
+func (x *ManageAdminsPrm) SetAdmin(key []byte) {
+	x.admin = key
+}
+
+// SetGroup sets identifier of the client group in a binary NeoFS API protocol format.
+// Makes sense only for client admins (see ManageAdminsPrm.SetClient).
+func (x *ManageAdminsPrm) SetGroup(id []byte) {
+	x.group = id
+}
+
+// ManageAdminsRes groups resulting values of node administer methods of Subnet contract.
+type ManageAdminsRes struct{}
+
+// ManageAdmins manages admin list of the NeoFS subnet through Subnet contract calls.
+func (x Client) ManageAdmins(prm ManageAdminsPrm) (*ManageAdminsPrm, error) {
+	var method string
+
+	args := make([]interface{}, 1, 3)
+	args[0] = prm.subnet
+
+	if prm.client {
+		args = append(args, prm.group, prm.admin)
+
+		if prm.rm {
+			method = "removeClientAdmin"
+		} else {
+			method = "addClientAdmin"
+		}
+	} else {
+		args = append(args, prm.admin)
+
+		if prm.rm {
+			method = "removeNodeAdmin"
+		} else {
+			method = "addNodeAdmin"
+		}
+	}
+
+	var prmInvoke client.InvokePrm
+
+	prmInvoke.SetMethod(method)
+	prmInvoke.SetArgs(args...)
+
+	err := x.client.Invoke(prmInvoke)
+	if err != nil {
+		return nil, err
+	}
+
+	return new(ManageAdminsPrm), nil
+}