API call to pull submission and push as media

[mathieubossaert]

We did implement this process last year and we described it here :

Updating external datasets from another form's submissions data from within a PostgreSQL database

I will first simply copy/adapt the push_json_media_to_central() function for csv files. I will try it by the end of the day and update the repo to add push_csv_media_to_central() function. In a second time will probably add a generic function to upload csv or geojson or xml attachments that checks the file extension to adapt the Content-type Header.

But in our common use cases the best way to update form attachments will soon be datasets and entities and we will use it as soon as possible instead of API form update.