Refactor appearances data to use a "body" object

This is more similar to what impress-2020 does, I was working on the
wardrobe-2020 code and took some inspiration!

The body has an ID and a species, or is the string "all".

app/models/item.rb

@@ -512,7 +512,8 @@ class Item < ApplicationRecord
     @parent_swf_asset_relationships_to_update = rels
   end
 
-  Appearance = Struct.new(:body_id, :swf_assets)
+  Body = Struct.new(:id, :species)
+  Appearance = Struct.new(:body, :swf_assets)
   def appearances
     all_swf_assets = swf_assets.to_a
 
@@ -525,7 +526,7 @@ class Item < ApplicationRecord
 
     # If there are no body-specific assets, return one appearance for them all.
     if swf_assets_by_body_id.empty?
-      return Appearance.new(0, swf_assets_for_all_bodies)
+      return Appearance.new(:all, swf_assets_for_all_bodies)
     end
 
     # Otherwise, create an appearance for each real (nonzero) body ID. We don't
@@ -533,7 +534,9 @@ class Item < ApplicationRecord
     # uhh, let's merge the body_id = 0 ones in?
     swf_assets_by_body_id.map do |body_id, body_specific_assets|
       swf_assets_for_body = body_specific_assets + swf_assets_for_all_bodies
-      Appearance.new(body_id, swf_assets_for_body)
+      species = Species.with_body_id(body_id).first!
+      body = Body.new(body_id, species)
+      Appearance.new(body, swf_assets_for_body)
     end
   end
 

app/models/species.rb

@@ -1,5 +1,6 @@
 class Species < ApplicationRecord
   translates :name
+  has_many :pet_types
   
   scope :alphabetical, -> {
     st = Species::Translation.arel_table
@@ -12,6 +13,11 @@ class Species < ApplicationRecord
       where(st[:name].matches(sanitize_sql_like(name)))
   }
 
+  scope :with_body_id, -> body_id {
+    pt = PetType.arel_table
+    joins(:pet_types).where(pt[:body_id].eq(body_id)).limit(1)
+  }
+
   # TODO: Should we consider replacing this at call sites? This used to be
   # built into the globalize gem but isn't anymore!
   def self.find_by_name(name)
@@ -19,7 +25,7 @@ class Species < ApplicationRecord
   end
   
   def as_json(options={})
-    {:id => id, :name => human_name}
+    super({only: [:id, :name], methods: [:human_name]}.merge(options))
   end
   
   def human_name