[#569] cli: Add control shards writecache seal command

It does the same as `control shards flush-writecache --seal`, but
has better name.

Signed-off-by: Dmitrii Stepanov <d.stepanov@yadro.com>

pkg/local_object_storage/shard/writecache.go

@@ -56,3 +56,33 @@ func (s *Shard) FlushWriteCache(ctx context.Context, p FlushWriteCachePrm) error
 
 	return s.writeCache.Flush(ctx, p.ignoreErrors, p.seal)
 }
+
+type SealWriteCachePrm struct {
+	IgnoreErrors bool
+}
+
+// SealWriteCache flushes all data from the write-cache and moves it to degraded read only mode.
+func (s *Shard) SealWriteCache(ctx context.Context, p SealWriteCachePrm) error {
+	ctx, span := tracing.StartSpanFromContext(ctx, "Shard.SealWriteCache",
+		trace.WithAttributes(
+			attribute.String("shard_id", s.ID().String()),
+			attribute.Bool("ignore_errors", p.IgnoreErrors),
+		))
+	defer span.End()
+
+	if !s.hasWriteCache() {
+		return errWriteCacheDisabled
+	}
+
+	s.m.RLock()
+	defer s.m.RUnlock()
+
+	if s.info.Mode.ReadOnly() {
+		return ErrReadOnlyMode
+	}
+	if s.info.Mode.NoMetabase() {
+		return ErrDegradedMode
+	}
+
+	return s.writeCache.Seal(ctx, p.IgnoreErrors)
+}