Change Rich Quoting HTML Format over the wire

[t3chguy]

To something a little richer that will look better on clients that do not yet support this feature whilst still keeping it as easy to parse

Fixes element-hq/element-web#5967
Fixes element-hq/element-web#5982

[t3chguy]

TravisCI Chrome is still broken

[dbkr]

I think we'll have to do the due diligence here as this is basically spec stuff (even if the actual blockquote / cite is going into org.matrix.custom.html). My main concern here is that the reply metadata is only in the HTML body, so clients that don't render HTML now have to parse the HTML body to support rich quoting. It feels like we ought to have the quoting metadata outside of the body, but then this is starting to intersect with @ara4n 's message typing stuff too.

Shall we get some suggestions on a google doc and try to get some feedback?

[t3chguy]

So I'm all for instead throwing quotedEvent: ".../..." into the content of the m.room.message, it'd mean that there can only be one, but I consider that a good thing
so that an event could not be sent with 100s of the damn things

[dbkr]

True, but in the context of a forum post, only being able to cite one message and in no particular point in your message feels quite limiting. I guess this is essentially the same argument as Pills where we eventually put everything into the HTML, so perhaps it's better to be consistent, although I still have the same concern there.

Anyway, arguing myself back & forth aside, unassigning myself to let others chime in.

[t3chguy]

Because of element-hq/element-web#5967 (comment) the semantics are entirely different IMO.
Its more a linear reply to a single precursor. So a replyingToEvent field on m.room.message events makes most sense for this to me. Though would mean that "dumb" clients would simply render nothing.

[t3chguy]

The above would also fix (and seems to be the sanest/only sane way to fix) things like: element-hq/element-web#6061

[t3chguy]

Could also fix node replacing nastiness/race conditions such as element-hq/element-web#6059 (comment)

[t3chguy]

Replaced by #1741