Add prereg line message to at-door registration

[khyperia]

WARNING: I'm not sure if this is overridden in production's config (as I think I don't have access to prod's config? I don't know how deployment works, hah). When merging this, please check to make sure it isn't.

Background: the at-door payment line is sometimes 15-30 minutes long, and pre-reg is usually instant or a couple minutes. I get really sad whenever someone waits 30 minutes to use the at-door table, when they could have just immediately picked up their badge in the prereg line.

[EliAndrewC]

+1 from me.

FWIW, our configuration is almost entirely public; we use Salt to deploy and "pillar data" which controls our configuration, which is both located and documented here:
https://github.com/magfest/infrastructure/tree/master/reggie_config

So for example I'm able to look in the following files:

• https://github.com/magfest/infrastructure/blob/master/reggie_config/super/init.yaml
• https://github.com/magfest/infrastructure/blob/master/reggie_config/super_2019/init.yaml
• https://github.com/magfest/infrastructure/blob/master/reggie_config/super_2019_prod/init.yaml

and confirm that we're not overriding door_payment_method anywhere. Furthermore, this does seem like the appropriate place to put this, since it seems like what we'd want to use as the general default value everywhere.

(The only pieces of config which are NOT stored in that public Git repo are passwords and API keys and such, which are stored in a non-public director on our Salt master.)

[kitsuta]

+1 from me as well, particularly with just changing the default instead of adding it to our config. I think it's reasonable to assume that any event that uses our at-door process (i.e., that lets attendees pay at the kiosk) would also have a similar line setup. I mean that's not actually true, but I still think it's a reasonable thing to assume. :P