unreal4 wants SID, not SERVER, for remote server introductions

[jesopo]

draft because this has only been tested live on pissnet so I'd like to run it by people more responsible than me

the problem here is SERVER is for direct server introductions and those expect passwords, so Atheme will be disconnected when it tries to jupe with SERVER due to "Missing password"

[kaniini]

generally we like to be explicit about the NULL check

[tzvetkoff]

I think I see a few potential problems here:

1. This algorithm will try generating sids like A00 after 9ZZ, which is invalid.
2. sid is static, meaning it will eventually exceed 9ZZ (even though nobody will run services that long and jupe that many servers.)

I also wonder why don't reuse the original server sid (if found) and only generate a new sid when one is proactively jupe'ing servers before they were even introduced?

[jesopo]

this SID generation was directly stolen from the other protocol modules

[kaniini]

this is correct other than the style change (or at least it was back in the ustream days)

[jesopo]

I think this is currently in a state that is technically correct and works but it will still fail on atypically complex networks (i.e. pissnet) and I'm not certain why. I think we ought to be doing this via SF_JUPE_PENDING a-la bahamut & inspircd but I've not been able to make that work; every time I defer an unreal4 jupe with this, atheme suddenly stops processing (or even debug logging) received SQUITs