Sprint 3 (Update main function + Log programs)

• ✅ elaborating commenters' connection by computing concurrency
• ✅ creating and separating dashboards (/dashboard, /overview, /keyword, /commenter)
• ✅ beautifying dashboards and making user-friendly (buttons to link each other, loading animation, and hint text)
• ✅ using Redis as cache to accelerate dashboard
• ✅ creating background server to update data in stored in Redis
• ✅ releasing three APIs (authors, keywords, ip address)
• ✅ setting mongo DB read preference to reduce burden on primary node
• ✅ deploying server (API + dashboard & background) to GCP
• ✅ logging airflow crawler and background server