232 upload file to folder

[tcnichol]

This pull request enabled users to upload files to a folder in a dataset through the api. Previously this option was not available.

The route api.Files.uploadToDataset now has a parameter folder_id: Option[String].

Swagger documentation for that route has also been updated.

[robkooper]

I think we can simplify (not tested)

val folder = folder_id.flatmap(x => folders.get(x))
val uploadedFiles = FileUtils.uploadFilesMultipart(request, Some(dataset), folder, showPreviews = showPreviews, originalZipFile = originalZipFile, flagsFromPrevious = flagsFromPrevious, runExtractors = extract, apiKey = request.apiKey) 
uploadedFiles.length match {
    case 0 => BadRequest("No files uploaded")
    case 1 => Ok(Json.obj("id" -> uploadedFiles.head.id))
    case _ => Ok(Json.obj("ids" -> uploadedFiles.toList))
}

This will use flatmap (if there is a value, return an option) to get the folder and then just call the next function with ether None, or Some(folder).

[tcnichol]

I am using the flatmap.

This works if folder_id is a UUID, and it works if folder_id is None, however, it breaks if folder_id is a string but not a UUID.

I know that there is a way to use conditionals inside of a flatMap, so I am trying to figure that out. Unless you know a quick fix offhand.

[tcnichol]

I am now using a conditional that seems to handle all cases without breaking.

Regrettably it kept giving me an error if I tried to put an Option[UUID] in the api route and didn't send it, but this seems to match what is done in a few other cases with optional uuid parameters.

[lmarini]

(This PR is not urgent, it can go in the next release) There is one issue mentioned below. Can you also please updated the changelog? Thank you!

[lmarini]

This throws an error if folder == None

[tcnichol]

I believe I have fixed this. Also updated changelog