Add a debugging statement for Authorization objects

acme.go

@@ -213,6 +213,7 @@ func (a *ACME) verifyAll(ctx context.Context, client *acme.Client, c *certConfig
 			return nil, fmt.Errorf("challenge type '%s' is not available", chal.Type)
 		}
 
+		log.Printf("attempting fulfillment for %q (identifier: %+v)", c.Names, z.Identifier)
 		for _, domain := range c.Names {
 			cleanup, err := v.Fulfill(ctx, client, domain, chal)
 			if err != nil {