Make errors used in cluster sync API unwrappable

Implement Unwrap() functions on sync package errors. This allows e.g.
retreiving the underlying error behind a sync.UnrecoverableSyncError

Signed-off-by: Angel Misevski <[email protected]>

Author: amisevsk

pkg/provision/sync/cluster_api.go

@@ -68,6 +68,10 @@ func (e *UnrecoverableSyncError) Error() string {
 	return e.Cause.Error()
 }
 
+func (e *UnrecoverableSyncError) Unwrap() error {
+	return e.Cause
+}
+
 // WarningError is returned when syncing is successful and can continue but there is a warning
 // regarding the objects synced to the cluster (e.g. they will not be updated)
 type WarningError struct {
@@ -81,3 +85,7 @@ func (e *WarningError) Error() string {
 	}
 	return e.Message
 }
+
+func (e *WarningError) Unwrap() error {
+	return e.Err
+}