Only fire !welcome once per named client

[Rixxan]

A cache system (similar to lookups) should be introduced so that the !welcome command (if args/client name is given) is only fired once per client. This will reduce spam in channel as well as confusion as to who is doing what.

Suggested format:

!welcome <--force> (clientName)

if no args, simply fire the !welcome without a name, thus avoiding pinging the user. This will probably use parts of https://gitlab.com/hull-seals/code/irc/halpybot/-/blob/develop/src/packages/edsm/edsm.py#L94-L100 as well as command masking from https://gitlab.com/hull-seals/code/irc/halpybot/-/blob/develop/src/commands/caseutils.py#L27

recommend also including a check for -LL where LL is a two-letter language code

[Rixxan]

This isn't a very common issue, and is questionable if we'll even want to/need to use this.

Worth discussion at a later time (post 1.5 launch)