Improve code quality by addressing TODO comments

[Akanksha-kedia]

Description

src/main/java/io/trino/gateway/ha/clustermonitor/ClusterStatsJdbcMonitor.java

• Change: Fix silent failure on invalid backend URL configuration
• Impact: Fail-fast behavior with descriptive error messages
• Lines: Replace return clusterStats.build() with throw new IllegalArgumentException()

src/test/java/io/trino/gateway/ha/security/TestOIDC.java

• Change: Replace System.out.println() with proper logging
• Impact: Professional logging practices in test code
• Lines: Add Logger import and replace print statement with log.info()

Additional context and related issues

Release notes

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