[#488] reputation/eigentrust/calculator: Implement calc wrapper

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

pkg/services/reputation/eigentrust/iteration.go

@@ -1,6 +1,8 @@
 package eigentrust
 
 import (
+	"context"
+
 	"github.com/nspcc-dev/neofs-node/pkg/services/reputation"
 )
 
@@ -25,7 +27,30 @@ func (x *EpochIteration) SetI(i uint32) {
 	x.i = i
 }
 
+func (x *EpochIteration) Increment() {
+	x.i++
+}
+
 type IterationTrust struct {
 	EpochIteration
 	reputation.Trust
 }
+
+// IterContext aggregates context and data required for
+// iterations.
+type IterContext struct {
+	context.Context
+	EpochIteration
+}
+
+func NewIterContext(ctx context.Context, epoch uint64, iter uint32) *IterContext {
+	ei := EpochIteration{}
+
+	ei.SetI(iter)
+	ei.SetEpoch(epoch)
+
+	return &IterContext{
+		Context:        ctx,
+		EpochIteration: ei,
+	}
+}