when downloaded from gallery, data files always receive extension csv

In reality, people may be uploading xlsx or other files. Extensions should not be renamed when downloading the files

[liside]

Well, the file has to be a csv. After they upload the file, the file will lose its extension so I need to rename it

[izaslavsky]

but the initial extension still shows in the gallery, as part of the file name?

[liside]

Renaming is meant to manage datasets, since users may have the same name for their datasets. If you want to keep it, we can keep it

[izaslavsky]

I think it would make more sense to rename things into dataset.csv, dataset_01.csv, dataset_02.csv, rather than changing extensions. When users see that it is an xsls file in the gallery (which is common for people who just started - and upload incorrect formats), click on it to download, get a csv file (while it is actually xlsx), try to open it as a csv, and get an error - we shall try to avoid this. When they upload a xlsx in the first place, the authoring should tell them that at this point only csv files are accepted

[liside]

I added a check block that stops users from uploading anything other than csv files