correctly send multiple expands as a comma seperated array

[niteshsandal-merge]

Summary

• Merge's REST API expects multi-value params like expand as CSV (?expand=groups,work_location), but the v4 SDK was serializing arrays as repeated params
  (?expand=groups&expand=work_location) — only the last value is respected, causing silent data loss
• Flatten top-level array query params to comma-separated strings in createRequestUrl before they reach the query string builder
• Added createRequestUrl.ts to .fernignore so the fix survives Fern regeneration