Store video files on external platform

[jo-elimu]

Description

Video files are too large to be stored directly in the database, so refactor the software to fetch videos from an external URL instead.

• Change IPFS URL to Pinata webapp#1945
• Move storage of videos from database to external platform webapp#1934
• Download videos from external platform content-provider#127

Why?

This is needed because the webapp crashes when there is a large collection of videos to be loaded from the database.