Bedhost: the user defined BED set download endpoint enhancement

[xuebingjie1990]

Users can define BED set by select and add bed files to the "BEDset cart" from the search result.
Users should be able to download the user defined BED set with download endpoint.
We use to have an endpoint that generate a .txt file of list of bedfile path. So user can bulk download bed files in the BED set with instructions given from the UI, for example: wget -i my_bedset_http.txt and cat my_bedset_s3.txt | parallel aws s3 cp {} <output_dir>

enhancement:

1. We would like the users to be able to download BED set as zip file
2. We would like the backend be able to processed the user defined BED set, and insert the stats into the database

[khoroshevskyi]

We should work more on this issue, as we don't have good way of doing it.

Idea: what if we will create temporary bedset in the database and then use bbconf to download it?