[#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/deps.go

@@ -0,0 +1,83 @@
+package trustcontroller
+
+import (
+	"context"
+	"io"
+
+	"github.com/nspcc-dev/neofs-node/pkg/services/reputation"
+)
+
+// Context wraps stdlib context
+// with accompanying meta values.
+type Context interface {
+	context.Context
+
+	// Must return epoch number to select the values.
+	Epoch() uint64
+}
+
+// Writer describes the interface for storing reputation.Trust values.
+//
+// This interface is provided by both local storage
+// of values and remote (wrappers over the RPC).
+type Writer interface {
+	// Write performs a write operation of reputation.Trust value
+	// and returns any error encountered.
+	//
+	// All values after the Close call must be flushed to the
+	// physical target. Implementations can cache values before
+	// Close operation.
+	//
+	// Put must not be called after Close.
+	Write(reputation.Trust) error
+
+	// Close exits with method-providing Writer.
+	//
+	// All cached values must be flushed before
+	// the Close's return.
+	//
+	// Methods must not be called after Close.
+	io.Closer
+}
+
+// WriterProvider is a group of methods provided
+// by entity which generates keepers of
+// reputation.Trust values.
+type WriterProvider interface {
+	// InitWriter should return an initialized Writer.
+	//
+	// Initialization problems are reported via error.
+	// If no error was returned, then the Writer must not be nil.
+	//
+	// Implementations can have different logic for different
+	// contexts, so specific ones may document their own behavior.
+	InitWriter(Context) (Writer, error)
+}
+
+// Iterator is a group of methods provided by entity
+// which can iterate over a group of reputation.Trust values.
+type Iterator interface {
+	// Iterate must start an iterator over all trust values.
+	// For each value should call a handler, the error
+	// of which should be directly returned from the method.
+	//
+	// Internal failures of the iterator are also signaled via
+	// an error. After a successful call to the last value
+	// handler, nil should be returned.
+	Iterate(reputation.TrustHandler) error
+}
+
+// IteratorProvider is a group of methods provided
+// by entity which generates iterators over
+// reputation.Trust values.
+type IteratorProvider interface {
+	// InitIterator should return an initialized Iterator
+	// that iterates over values from IteratorContext.Epoch() epoch.
+	//
+	// Initialization problems are reported via error.
+	// If no error was returned, then the Iterator must not be nil.
+	//
+	// Implementations can have different logic for different
+	// contexts, so specific ones may document their own behavior.
+	InitIterator(Context) (Iterator, error)
+}