nctalk: Add option to use User ID instead of Display Name as nick

[s3lph]

As proposed in #1250.

Use case: The Nextcloud instance I intend to use this with gets its user accounts from an LDAP directory with nicknames as UIDs and full names as display names. However, in channels which are bridged to public IRC, I'd prefer to use nicknames rather than full names.

This change only applies to non-guest users, as guests are already handled specially and their UIDs are long hex strings (like 4247797f3cbf4fb2f4ee73995f2a2c683d32284e), which is quite unfit for display.

[gary-kim]

LGTM. I have one suggestion if you want to implement it but your choice :)

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[42wim]

I've been thinking about this, I think it's better we fix this in a general way instead of adding yet another config option.

What about we add {USERID} (and {USERNAME} as an alias to {NICK}) as an option in RemoteNickFormat?
(and in future also {USERDISPLAYNAME} etc ..)

[s3lph]

Come to think of it, this does sound like the more sensible approach. I just had a look at the code, the nctalk bridge already uses the same value as config.Message.UserID, so this would work.

However, there's still the issue with nctalk's guest users, their random ID still needs to be covered. Also, if more keys are introduced in the future, the RemoteNickFormat interpolation logic probably needs to be at least partially moved to the individual bridges.

[s3lph]

I had some more thoughts about how to best implement this: I agree that it would be a good solution to extend the RemoteNickFormat. However, due to the special handling required for nctalk guest users, I think in this case this approach makes more sense.