[#1074] neofs-cli: Move session preparation to modules/session package

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

cmd/neofs-cli/internal/commonflags/session.go

@@ -0,0 +1,14 @@
+package commonflags
+
+import "github.com/spf13/cobra"
+
+const SessionToken = "session"
+
+// InitSession initializes session parameter for cmd.
+func InitSession(cmd *cobra.Command) {
+	cmd.Flags().String(
+		SessionToken,
+		"",
+		"path to a JSON-encoded container session token",
+	)
+}