Get video converter working

[nngerncham]

Converter must be able to:

• [ ] Fetch video data from the database
• [x] Download file from raw S3 store
• [x] Convert raw video into chunking-supporting format
• [x] Upload file back to converted S3 store

File format specs:

• H.264/ MPEG-4 AVC seems to be most popular
• H.265 has started replacing H.264 so might play around with that source: https://imagekit.io/blog/video-file-formats/

[nngerncham]

Decided against fetching video data from the database and any operation involving the database will be done in the backend.