[Feature Request] Remote-Playlists

Hello Libretro Team,

it would be great to define "Remote-Playlists", which could Download the Content-Files from a Webserver.
The Idea is the following, in the "Import Content" Menu would be a new Entry "Remote Content".

There would be then the following entries:

• Content-Items URL: thats a URL from where a JSON-File should be downloaded with the Items, I append an example below.
• Username: Optional User Field for a basic authentication
• Password: Optional Password for a basic authentication
• System Name: Analog to the "Manual Scan" a selection of the following entries: , & and the Databases
• Custom System Name: Analog to the "Manual Scan" a field for the Custom-Name
• Default Core: Analog to the "Manual Scan" an option to choose the Core for the Content
• Start Scan or Create: Which would Download the JSON-File and would create the Playlist then.

Here is an Example of the JSON-File which i think it could handle every relevant action.

{
    "version": "1.0",
    "items": [
        {
            "url": "http://my-server-ip/ROMs/SNES/Diddy's Kong Quest (D, F, E).smc",
            "file_name": "Diddy's Kong Quest (D, F, E).sfc",
            "label": "Donkey Kong Country",
            "thumbnail_boxart_url": "http://my-server-ip/ROMs/SNES/Diddy's Kong Quest (D, F, E).png",
            "thumbnail_snap_url": "http://my-server-ip/ROMs/SNES/Diddy's Kong Quest (D, F, E)-snap.png",
            "thumbnail_title_url": "http://my-server-ip/ROMs/SNES/Diddy's Kong Quest (D, F, E)-title.png"
        }
    ]
}

Where I think the Thumbnail-Fields should be optional (just to download them if the are defined).

Or it could also be an option to have the url and file_name fields as array in plural to support multi-disc or multi-file roms:

{
    "version": "1.0",
    "items": [
        {
            "urls": [
                "http://my-server-ip/ROMs/PSX/Resident Evil.cue",
                "http://my-server-ip/ROMs/PSX/Resident Evil.bin"
            ],
            "file_names": [
                "Resident Evil.cue",
                "Resident Evil.bin"
            ],
            "label": "Resident Evil",
            "thumbnail_boxart_url": "http://my-server-ip/ROMs/PSX/Resident Evil.png"
        }
    ]
}

It would be nice when I create the playlist in the Retro-Arch, it would download the JSON and the Optional Thumbnails with the right naming conventions.
When I first want to launch a game from an "Remote Playlist" it should download the Content-File(s) from the URL(s) (probably in the "download" folder or a subfolder which already is used for the Cloud-Sync-Process). It should check always if the file already exists and probably redownload it.

This would be a feature which could solve 2 goals for me (and I think for others to ;)).

1. One central place to manage all ROMs with multiple Client-Devices (Smartphone, Apple-TV, Laptop, and so on).
2. On an Apple-TV when Apple decides there is not enough space left and delete some files, i haven't to care because the file would be redownloaded when the game is started the next time.

I hope you think this is useful and best regards
Alec4

Start with the Import Content menu and the existing Manual Scan flow; the issue provides no file or test pointers. Map how playlists, JSON parsing, authentication, downloads, thumbnails, and launch-time content retrieval are currently handled. Done would require an agreed schema and support for playlist creation plus deferred downloads for single- and multi-file items.