api: make IP addresses in the API.

Make the following fields visible in API responses:

* ip_bans.ip_addr
* ip_geolocations.ip_addr
* ip_geolocations.network
* users.last_ip_addr (mod only)
* user_sessions.ip_addr
* api_keys.last_ip_address
* api_keys.permitted_ip_addresses

Before IP addresses were globally hidden in API responses because IPs were
present in a lot of tables and we didn't want to accidentally leak them.
Now that we've gotten rid of IPs from most tables, it's safe to unhide them.

app/models/ip_ban.rb

@@ -1,6 +1,8 @@
 # frozen_string_literal: true
 
 class IpBan < ApplicationRecord
+  attribute :ip_addr, :ip_address
+
   belongs_to :creator, class_name: "User"
 
   validate :validate_ip_addr
@@ -23,7 +25,7 @@ class IpBan < ApplicationRecord
   end
 
   def self.ip_matches(ip_addr)
-    where("ip_addr >>= ?", ip_addr)
+    where("ip_addr >>= ?", ip_addr.to_s)
   end
 
   def self.hit!(category, ip_addr)
@@ -62,7 +64,7 @@ class IpBan < ApplicationRecord
   def validate_ip_addr
     if ip_addr.blank?
       errors.add(:ip_addr, "is invalid")
-    elsif ip_addr.private? || ip_addr.loopback? || ip_addr.link_local?
+    elsif ip_addr.is_local?
       errors.add(:ip_addr, "must be a public address")
     elsif full_ban? && ip_addr.ipv4? && ip_addr.prefix < 24
       errors.add(:ip_addr, "may not have a subnet bigger than /24")
@@ -72,25 +74,11 @@ class IpBan < ApplicationRecord
       errors.add(:ip_addr, "may not have a subnet bigger than /48")
     elsif partial_ban? && ip_addr.ipv6? && ip_addr.prefix < 20
       errors.add(:ip_addr, "may not have a subnet bigger than /20")
-    elsif new_record? && IpBan.active.where(category: category).ip_matches(subnetted_ip).exists?
+    elsif new_record? && IpBan.active.where(category: category).ip_matches(ip_addr).exists?
       errors.add(:ip_addr, "is already banned")
     end
   end
 
-  def has_subnet?
-    (ip_addr.ipv4? && ip_addr.prefix < 32) || (ip_addr.ipv6? && ip_addr.prefix < 128)
-  end
-
-  def subnetted_ip
-    str = ip_addr.to_s
-    str += "/" + ip_addr.prefix.to_s if has_subnet?
-    str
-  end
-
-  def ip_addr=(ip_addr)
-    super(ip_addr.strip)
-  end
-
   def self.available_includes
     [:creator]
   end

app/models/user.rb

@@ -67,7 +67,7 @@ class User < ApplicationRecord
   attribute :inviter_id
   attribute :last_logged_in_at, default: -> { Time.zone.now }
   attribute :last_forum_read_at, default: "1960-01-01 00:00:00"
-  attribute :last_ip_addr
+  attribute :last_ip_addr, :ip_address
   attribute :comment_threshold, default: -8
   attribute :default_image_size, default: "large"
   attribute :favorite_tags