feat: Optional filename prefix for tracks

[jongirard]

As @sgfn mentioned over in #194, I'm aware the recorder ecosystem is in a delicate state right now with limited bandwidth for broader changes, however, I currently have a need within my project to support a known identifier in created recordings (which I believe may be a use case others will encounter as well).

This minor change will allow for an optional prefix to be used in a track's filename (such as user id) which is useful for associating the arbitrary track ID with a known identifier (ex: e0bc96adf4-19760930259463780812500431447.rtpx (user_id-track_id).

Thank you for considering this change!

[sgfn]

Thanks for the suggestion. We'll make sure to add the possibility of including custom metadata together with the recordings in 0.9.0

You can track the progress in #197 :)

[jongirard]

@sgfn thanks, ideally the metadata can be per track like this, not simply at the room level. This gives the ultimate flexibility imo. I also personally like having the prefix in the filename too because it's easy to observe at a high level/in a folder hierarchy. Coupled with the option to include a metadata map for any other extra fields in the reports.json which could be nice.