[#356] refs: Handle uint32 overflow in `SubnetID` text format

Clarify the bit size limit in `SubnetID.UnmarshalText` method. Cover
overflow case in unit test.

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

refs/types.go

@@ -199,7 +199,9 @@ func (s *SubnetID) MarshalText() ([]byte, error) {
 }
 
 // UnmarshalText decodes SubnetID from the text according to NeoFS API V2 protocol:
-// should be base-10 integer string format.
+// should be base-10 integer string format with bitsize = 32.
+//
+// Returns strconv.ErrRange if integer overflows uint32.
 //
 // Must not be called on nil.
 //

refs/types_test.go

@@ -1,6 +1,7 @@
 package refs_test
 
 import (
+	"math"
 	"strconv"
 	"testing"
 
@@ -47,4 +48,13 @@ func TestSubnetID_UnmarshalText(t *testing.T) {
 	require.NoError(t, err)
 
 	require.EqualValues(t, val, id.GetValue())
+
+	t.Run("uint32 overflow", func(t *testing.T) {
+		txt := strconv.FormatUint(math.MaxUint32+1, 10)
+
+		var id refs.SubnetID
+
+		err := id.UnmarshalText([]byte(txt))
+		require.ErrorIs(t, err, strconv.ErrRange)
+	})
 }