ip addresses: move more logic to Danbooru::IpAddress.

* Move `is_local?` from IpLookup to Danbooru::IpAddress.
* Refactor more things to use Danbooru::IpAddress instead of using
  IPAddress directly.

app/logical/danbooru/ip_address.rb

@@ -5,10 +5,23 @@
 module Danbooru
   class IpAddress
     attr_reader :ip_address
-    delegate_missing_to :ip_address
+    delegate :ipv4?, :ipv6?, :loopback?, :link_local?, :unique_local?, :private?, :to_string, :prefix, :multicast?, :unspecified?, to: :ip_address
+    delegate :ip_info, :is_proxy?, to: :ip_lookup
 
     def initialize(string)
-      @ip_address = ::IPAddress.parse(string)
+      @ip_address = ::IPAddress.parse(string.to_s)
+    end
+
+    def ip_lookup
+      @ip_lookup ||= IpLookup.new(self)
+    end
+
+    def is_local?
+      if ipv4?
+        loopback? || link_local? || multicast? || private?
+      elsif ipv6?
+        loopback? || link_local? || unique_local? || unspecified?
+      end
     end
 
     # "1.2.3.4/24" if the address is a subnet, "1.2.3.4" otherwise.
@@ -19,5 +32,17 @@ module Danbooru
     def inspect
       "#<Danbooru::IpAddress #{to_s}>"
     end
+
+    def ==(other)
+      self.class == other.class && to_s == other.to_s
+    end
+
+    # This is needed to be able to correctly treat IpAddresses as hash keys,
+    # which Rails does internally when preloading associations.
+    def hash
+      to_s.hash
+    end
+
+    alias_method :eql?, :==
   end
 end