[release-0.20] 🐛 Check to see if custom source implements fmt.Stringer when logging (#3077)

* add String() to source interface Signed-off-by: Troy Connor <troy0820@users.noreply.github.com> * remove the enforcement of fmt.Stringer --------- Signed-off-by: Troy Connor <troy0820@users.noreply.github.com> Co-authored-by: Troy Connor <troy0820@users.noreply.github.com>

Author: k8s-infra-cherrypick-robot

pkg/internal/controller/controller.go

@@ -175,7 +175,16 @@ func (c *Controller[request]) Start(ctx context.Context) error {
 // caches.
 errGroup := &errgroup.Group{}
 for _, watch := range c.startWatches {
-log := c.LogConstructor(nil).WithValues("source", fmt.Sprintf("%s", watch))
+log := c.LogConstructor(nil)
+_, ok := watch.(interface {
+String() string
+})
+
+if !ok {
+log = log.WithValues("source", fmt.Sprintf("%T", watch))
+} else {
+log = log.WithValues("source", fmt.Sprintf("%s", watch))
+}
 didStartSyncingSource := &atomic.Bool{}
 errGroup.Go(func() error {
 // Use a timeout for starting and syncing the source to avoid silently