[#428] reputation: Implement local trust controller

Implement `Controller` designed to analyze the values collected by the local
node (the source is hidden behind Writer/WriterProvider interfaces) and
transfer them to the destination (hidden behind Iterator / IteratorProvider
interface).

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

pkg/services/reputation/local/controller/util.go

@@ -0,0 +1,30 @@
+package trustcontroller
+
+type storageWrapper struct {
+	w Writer
+	i Iterator
+}
+
+func (s storageWrapper) InitIterator(Context) (Iterator, error) {
+	return s.i, nil
+}
+
+func (s storageWrapper) InitWriter(Context) (Writer, error) {
+	return s.w, nil
+}
+
+// SimpleIteratorProvider returns IteratorProvider that provides
+// static context-independent Iterator.
+func SimpleIteratorProvider(i Iterator) IteratorProvider {
+	return &storageWrapper{
+		i: i,
+	}
+}
+
+// SimpleWriterProvider returns WriterProvider that provides
+// static context-independent Writer.
+func SimpleWriterProvider(w Writer) WriterProvider {
+	return &storageWrapper{
+		w: w,
+	}
+}