Lower API cost of refreshing videos

[eliihen]

I am currently hitting the resource cap with my 70+ subscriptions, and it is triggering other issues like #2. We should figure out some way to reduce the API resource usage to scale better.

Currently the app has a local database to store the metadata of all videos that have been fetched. Then it runs a "cron"-job every 5 minutes which does a search on each channel you have subscribed to. This fetches the most recent videos and updates the db, but is also very intense in terms of API usage and does not scale very well. Can we do this some better way?