Guard undefined handler.identifiers in keywordPreservation.ts

[TimeTravelerFromNow]

🔧 Changes

This rescues an error in src/keywordPreservation.ts when handler.identifiers is undefined
#1446

📚 References

Uses @rdroe 's suggested fix Option B described in #1446

Option B — skip handlers without identifiers:

if (handler.identifiers === undefined) return acc;
acc[handler.type] = handler.identifiers.flat();

🔬 Testing

With AUTH0_PRESERVE_KEYWORDS: true in config, perform an export for example like so:

npx auth0-deploy-cli export \
  --strip \
  --format directory \
  --output_folder ./${output_folder} \
  --config_file ./${output_folder}/${from_tenant}.json \
  --debug true

📝 Checklist

• All new/changed/fixed functionality is covered by tests (or N/A)
• [N/A] I have added documentation for all new/changed functionality (or N/A)