Document that config/*.yml settings don't get used by omnibus

From Slack:

godfat [10:45 PM] 
Sorry for misleading you :o should we update mail_room.yml to make this more obvious? Maybe don't set the default there if it doesn't have effect? (I am still not very sure how all configs get together)

chris [10:47 PM] 
@godfat: No problemo! Regarding the defaults, the default in the gitlab-ce `mail_room.yml` will have an effect on source installations. Omnibus is handled by the cookbook.. ​˜I think˜​…  @stanhu (edited)

stanhu [10:48 PM] 
The CE mail_room.yml will not have an effect, you mean

chris [10:48 PM] 
The CE `mail_room.yml` is used for source installations ?

[10:48] 
:confused:

stanhu [10:49 PM] 
yes and dev environments
omnibus owns all the config files

godfat [10:50 PM] 
Does that mean anything in CE config don't have an effect for omnibus installation?

stanhu [10:52 PM] 
@godfat config/intiailizers/1_settings.rb is the only place that influences the config from omnibus

godfat [10:53 PM] 
@stanhu: I see, I assume it's because it's an initializer (being executed anyway)

stanhu [10:56 PM] 
where shall we document this? :slightly_smiling_face:

godfat [10:57 PM] 
That would be nice. Not sure where to document though. Maybe in gitlab. yml?

stanhu [10:58 PM] 
maybe a README.md in gitlab-ce/config dir?