Feature request: play uploaded file

[AGSPhoenix]

A few users on my server want to be able to just post MP3s and have the bot play them out. It seems like a blank ::play call with the file attached would be a pretty simple way to do so.

Security considerations:

• This ability should default to off, and require configuration changes to enable. lavaplayer and ukulele are not bug free, and probably contain vulnerabilities that could be exploited with enough effort. Bot operators should have to opt in to that risk.
• As an extra spicy config option, the ability to fetch MP3s from an arbitrary URL would be a moderately useful bonus, as long as you aren't worried about your users setting up a server to get the bot's IP address. Would be something like ::play https://example.com/muzak.mp3

For a first implementation, it might be best to have the bot fetch the full file before playing (Maybe cap it at 100 MB for non-Discord links?). Some servers will disconnect clients downloading slowly, or won't support resuming a transfer, which would cut the playback off several minutes in. Not sure if Discord's CDN does this. Might not even be necessary? Could use some testing.

Freya, any objections to this functionality? Kinda toying with the idea of writing this up into a PR.

[freyacodes]

I believe that linking URLs will just attempt to play any audio the bot finds. This is done by streaming, which doesn't seem to be a common issue. Streaming also supports the use of internet radios.

Grabbing any attachment URL to use instead would be very easy.

The configuration properties you mentioned could also be implemented.