[redpanda] sasl test for wrong mechanism (#2048)

* [redpanda] sasl test, wrong mechanism

- ensure that when using a different sasl mechanism from the broker,
  unsupported error is returned

* chore: use require

---------

Co-authored-by: Manuel de la Peña <mdelapenya@gmail.com>
Co-authored-by: Manuel de la Peña <social.mdelapenya@gmail.com>

modules/redpanda/redpanda_test.go

@@ -16,6 +16,7 @@ import (
 	"github.com/twmb/franz-go/pkg/kadm"
 	"github.com/twmb/franz-go/pkg/kerr"
 	"github.com/twmb/franz-go/pkg/kgo"
+	"github.com/twmb/franz-go/pkg/sasl/plain"
 	"github.com/twmb/franz-go/pkg/sasl/scram"
 
 	"github.com/testcontainers/testcontainers-go"
@@ -162,6 +163,23 @@ func TestRedpandaWithAuthentication(t *testing.T) {
 		require.ErrorContains(t, err, "SASL_AUTHENTICATION_FAILED")
 	}
 
+	// Test wrong mechanism
+	{
+		kafkaCl, err := kgo.NewClient(
+			kgo.SeedBrokers(seedBroker),
+			kgo.SASL(plain.Auth{
+				User: "no-superuser",
+				Pass: "test",
+			}.AsMechanism()),
+		)
+		require.NoError(t, err)
+
+		kafkaAdmCl := kadm.NewClient(kafkaCl)
+		_, err = kafkaAdmCl.Metadata(ctx)
+		require.Error(t, err)
+		require.ErrorContains(t, err, "UNSUPPORTED_SASL_MECHANISM")
+	}
+
 	// Test Schema Registry API
 	httpCl := &http.Client{Timeout: 5 * time.Second}
 	// schemaRegistryAddress {