[#446] los: Wrap SSD errors in a separate type

Signed-off-by: Evgenii Stratonikov <e.stratonikov@yadro.com>

pkg/local_object_storage/internal/metaerr/error.go

@@ -0,0 +1,33 @@
+package metaerr
+
+import "errors"
+
+// Error is a wrapper for SSD-related errors.
+// In our model it unites metabase, pilorama and write-cache errors.
+type Error struct {
+	err error
+}
+
+// New returns simple error with a provided error message.
+func New(msg string) Error {
+	return Error{err: errors.New(msg)}
+}
+
+// Error implements the error interface.
+func (e Error) Error() string {
+	return e.err.Error()
+}
+
+// Wrap wraps arbitrary error.
+// Returns nil if err == nil.
+func Wrap(err error) error {
+	if err != nil {
+		return Error{err: err}
+	}
+	return nil
+}
+
+// Unwrap returns underlying error.
+func (e Error) Unwrap() error {
+	return e.err
+}