[idea] Dynamically loading course in new semester upon user request

[William-An]

What is this idea related to?

backend

Is your feature request related to a problem? Please describe.

1. Upon new semester, using crawler and manually update db is a lot of work
2. Some schools will update courses schedule during of days before the semester begin

Describe the solution you'd like

1. Create a middleware to send the course user requested to school server if the newest copy is not presented
2. Use these middleware as background worker? #89