Add option to record a cassette starting from offset/timestamp (and optionally ending with an offset/timestamp)

[schrepfler]

Would be nice to be able to record a cassette base from an existing topic by specifying from when (and optionally until when) based on offsets or timestamps.

[le-grimpeur]

Hey , I think if you create a group with specific offset before you lauch the record and when you lauch it you specify the group id, it will record at the start of the offset.