[fix][broker] Apply the role logging anonymizer to topic authorization denial logs - #26642

Motivation

PIP-402 added authenticationRoleLoggingAnonymizer so operators can keep roles out of broker logs.
The warning ServerCnx.isTopicOperationAllowed logs when a topic operation is not allowed still
printed authRole and originalPrincipal as is.

DefaultAuthenticationRoleLoggingAnonymizer.anonymize(null) also failed with the SHA256 and MD5
anonymizers, while originalPrincipal is null for every client that does not connect through a proxy.

Modifications

• Pass authRole and originalPrincipal through the anonymizer in the topic authorization denial log.
• Return null from DefaultAuthenticationRoleLoggingAnonymizer.anonymize for a null role.

Verifying this change

• Make sure that the change passes the CI checks.

This change added tests and can be verified as follows:

• Added DefaultAuthenticationRoleLoggingAnonymizerTest, covering a null role for every anonymizer
  type and the anonymized value of a role.

Does this pull request potentially affect one of the following parts:

• Dependencies (add or upgrade a dependency)
• The public API
• The schema
• The default values of configurations
• The threading model
• The binary protocol
• The REST endpoints
• The admin CLI options
• The metrics
• Anything that affects deployment

🤖 Generated with Claude Code