Each dmail creates two copies, one for the sender and one for the
receiver. Only spam check the receiver's copy.
Prevents senders from being able to tell when their messages are being
spam filtered.
Bug introduced in 1400f64; that commit changed dmails so that
creator_ip_addr defaulted to CurrentUser.ip_addr like this:
after_initialize :initialize_attributes, if: :new_record?
def initialize_attributes
self.from_id ||= CurrentUser.id
self.creator_ip_addr ||= CurrentUser.ip_addr
end
...but creator_ip_addr already defaulted to 127.0.0.1 from the database,
so the ||= assignment didn't work. Remove the database default so we
always default to CurrentUser.ip_addr.
There's not much sense in saving copies of everything DanbooruBot sends
in DanbooruBot's inbox. They probably won't be checked so it just bloats
the dmails table.
