[#189] sdk/netmap: Refactor Clause enum

Replace alias to v2 type Clause with v2-compatible implementation.

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

pkg/netmap/clause.go

@@ -0,0 +1,54 @@
+package netmap
+
+import (
+	"github.com/nspcc-dev/neofs-api-go/v2/netmap"
+)
+
+// Clause is an enumeration of selector modifiers
+// that shows how the node set will be formed.
+type Clause uint32
+
+const (
+	_ Clause = iota
+
+	// ClauseSame is a selector modifier to select only nodes having the same value of bucket attribute.
+	ClauseSame
+
+	// ClauseDistinct is a selector modifier to select nodes having different values of bucket attribute.
+	ClauseDistinct
+)
+
+// ClauseFromV2 converts v2 Clause to Clause.
+func ClauseFromV2(c netmap.Clause) Clause {
+	switch c {
+	default:
+		return 0
+	case netmap.Same:
+		return ClauseSame
+	case netmap.Distinct:
+		return ClauseDistinct
+	}
+}
+
+// ToV2 converts Clause to v2 Clause.
+func (c Clause) ToV2() netmap.Clause {
+	switch c {
+	default:
+		return netmap.UnspecifiedClause
+	case ClauseDistinct:
+		return netmap.Distinct
+	case ClauseSame:
+		return netmap.Same
+	}
+}
+
+func (c Clause) String() string {
+	switch c {
+	default:
+		return "UNSPECIFIED"
+	case ClauseDistinct:
+		return "DISTINCT"
+	case ClauseSame:
+		return "SAME"
+	}
+}