channels: resend the last 10 messages on joining

[r10s]

as discussed internally in different one-to-ones, channels will improve hugely, when resending the last some messages when a new subscriber joins - currently, they have an empty chat, not even the idea if things are working or not.

the same idea is around for groups as well, but for channels it is far easier and the tools mostly exist:

• we have already a resend() function
• we do not come into the situation to resend "on behalf of others"
• the question of privacy, of ppl not wanting history to be exposed to new members, is far less than in a normal group (even there questionable)

so, actionable item:

on adding a new subscriber, call resend() for the last 10 messages.

we can improve and iterate on that, eg. resending always webxdc - but for that, webxdc should start working at all

cmp #7679, #7680

cc @Hocuri

[Simon-Laux]

on adding a new subscriber, call resend() for the last 10 messages.

we can improve and iterate on that

resend sends it also to all existing members I guess, so we should create an issue to optimize sending to only send to new member, because re-sending in huge channels may result in quite some traffic. (though that traffic is probably mostly limited to the email network, end users wouldn't download a message that they already have - so not much extra traffic for end users)

[r10s]

resend sends it also to all existing members I guess, so we should create an issue to optimize sending to only send to new member

that indeed sounds easy enough to go for that