fix: handle NumberFormatException in ClassifiedListingEventDeserializer

[Copilot]

Summary

ClassifiedListingEventDeserializer had unguarded Integer.parseInt() and Long.parseLong() calls that could throw uncaught exceptions on malformed JSON input.

Type of change

• fix - Bug fix (non-breaking)

What changed?

Added fail-fast validation and exception handling:

String kindValue = generalMap.get("kind");
String createdAtValue = generalMap.get("created_at");

try {
  if (kindValue == null) {
    throw new IOException("Missing required field 'kind' in ClassifiedListingEvent");
  }
  if (createdAtValue == null) {
    throw new IOException("Missing required field 'created_at' in ClassifiedListingEvent");
  }
  
  int kindInt = Integer.parseInt(kindValue);
  long createdAt = Long.parseLong(createdAtValue);
  // ... rest of deserialization
} catch (NumberFormatException ex) {
  throw new IOException(
    String.format(
      "Failed to parse numeric field in ClassifiedListingEvent - kind='%s', created_at='%s': %s",
      kindValue, createdAtValue, ex.getMessage()),
    ex);
}

Changes:

• Null checks for required fields before parsing
• NumberFormatException → IOException with field context
• Error messages include field names and values for debugging

Breaking changes

None.

Testing

• Unit tests pass: mvn test
• Integration tests pass: mvn verify (requires Docker)
• CodeQL security scan: 0 alerts

Review focus

Error message format provides sufficient context for debugging malformed events?

Checklist

• PR title follows conventional commits: type(scope): description
• Changes are focused and under 300 lines (or stacked PRs)
• Tests added/updated for new functionality
• No new compiler warnings introduced
• CHANGELOG.md updated (for user-facing changes)

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