Act: play file, and handling of file to voice channel

[passcod]

{ "play": {
	"uri": "/static/bell.mp4"
} }

{ "play": {
	"uri": "/static/bell.mp4",
    "duration": 2000,
    "offset": 500,
    "delay": 15000
} }

{ "play": {
	"uri": "/static/bell.mp4",
    "at": "2020-11-08T12:34:56Z"
} }