Add MutualTls authenticators to defaultApprovedAuthenticators

Allow MutualTlsWithPasswordFallbackAuthenticator and
MutualTlsAuthenticator as possible authenticators.

MutualTlsWithPasswordFallbackAuthenticator should behave
functionally the same as PasswordAuthenticator.

MutualTlsAuthenticator's current implementation doesn't send
AUTHENTICATE messages to the client, but felt it was worth
including here in case it is ever enhanced to possibly
also require credentials.

patch by Andy Tolbert; reviewed by <Reviewers> for CASSANDRA-19858

Author: tolbertam

conn.go

@@ -46,6 +46,8 @@ import (
 var (
 	defaultApprovedAuthenticators = []string{
 		"org.apache.cassandra.auth.PasswordAuthenticator",
+		"org.apache.cassandra.auth.MutualTlsAuthenticator",
+		"org.apache.cassandra.auth.MutualTlsWithPasswordFallbackAuthenticator",
 		"com.instaclustr.cassandra.auth.SharedSecretAuthenticator",
 		"com.datastax.bdp.cassandra.auth.DseAuthenticator",
 		"io.aiven.cassandra.auth.AivenAuthenticator",

conn_test.go

@@ -56,6 +56,8 @@ const (
 func TestApprove(t *testing.T) {
 	tests := map[bool]bool{
 		approve("org.apache.cassandra.auth.PasswordAuthenticator", []string{}):                                          true,
+		approve("org.apache.cassandra.auth.MutualTlsWithPasswordFallbackAuthenticator", []string{}):                     true,
+		approve("org.apache.cassandra.auth.MutualTlsAuthenticator", []string{}):                                         true,
 		approve("com.instaclustr.cassandra.auth.SharedSecretAuthenticator", []string{}):                                 true,
 		approve("com.datastax.bdp.cassandra.auth.DseAuthenticator", []string{}):                                         true,
 		approve("io.aiven.cassandra.auth.AivenAuthenticator", []string{}):                                               true,