investigate channel detach functionality

[slingamn]

https://wiki.znc.in/Detaching

Let's investigate how hard this would be. It seems like it should be per-session (but is that how ZNC does it?). One challenge is disconnecting while detached and then reconnecting: you should receive the messages that were played on that channel while you were detached, but your lastseen timestamp will be ahead of this. (Is there a way to do this without maintaining per-channel, per-session lastseen timestamps?)

[brettgilio]

Additionally, maybe Ergo would implement a method of showing who is detached from a channel by marking nick[d]