Make Kerberos realm configurable in HBaseStorageBackend

[em3s]

Summary

The Kerberos principal realm is hardcoded to @KAKAO.HADOOP in HBaseStorageBackend.kt, which couples the code to a specific organization's Kerberos realm and may cause authentication failures in other environments.

Current Behavior

// HBaseStorageBackend.kt:117-118
config["hbase.master.kerberos.principal"] = "hbase/_HOST@KAKAO.HADOOP"
config["hbase.regionserver.kerberos.principal"] = "hbase/_HOST@KAKAO.HADOOP"

Expected Behavior

The Kerberos realm should be configurable via properties:

val kerberosRealm = properties["kerberos.realm"] 
    ?: throw IllegalStateException("Kerberos realm is not set for secure cluster")
config["hbase.master.kerberos.principal"] = "hbase/_HOST@$kerberosRealm"
config["hbase.regionserver.kerberos.principal"] = "hbase/_HOST@$kerberosRealm"

Impact

• Users outside of Kakao cannot use secure HBase clusters without modifying source code
• Makes the project less portable for open source adoption

Suggested Implementation

1. Add kerberos.realm property to the configuration
2. Update documentation to include the new property
3. Consider providing a sensible default or requiring explicit configuration for secure clusters

Related

Found during code review of PR #175 (StorageBackend abstraction layer)