posts: eliminate pool_id, favgroup_id url params.

Replace the `pool_id` and `favgroup_id` url params:

    https://danbooru.donmai.us/posts/123?pool_id=456
    https://danbooru.donmai.us/posts/123?favgroup_id=456

with the `q` param:

    https://danbooru.donmai.us/posts/123?q=pool:456
    https://danbooru.donmai.us/posts/123?q=favgroup:456

app/components/post_navbar_component.rb

@@ -1,14 +1,10 @@
 class PostNavbarComponent < ApplicationComponent
-  extend Memoist
+  attr_reader :post, :current_user, :search
 
-  attr_reader :post, :current_user, :search, :pool_id, :favgroup_id
-
-  def initialize(post:, current_user:, search: nil, pool_id: nil, favgroup_id: nil)
+  def initialize(post:, current_user:, search: nil)
     @post = post
     @current_user = current_user
     @search = search.presence || "status:any"
-    @pool_id = pool_id&.to_i
-    @favgroup_id = favgroup_id&.to_i
   end
 
   def render?
@@ -16,24 +12,30 @@ class PostNavbarComponent < ApplicationComponent
   end
 
   def pools
-    post.pools.undeleted.sort_by do |pool|
+    @pools ||= post.pools.undeleted.sort_by do |pool|
       [pool.id == pool_id ? 0 : 1, pool.is_series? ? 0 : 1, pool.name]
     end
   end
 
   def favgroups
-    current_user.favorite_groups.for_post(post.id).sort_by do |favgroup|
+    @favgroups ||= current_user.favorite_groups.for_post(post.id).sort_by do |favgroup|
       [favgroup.id == favgroup_id ? 0 : 1, favgroup.name]
     end
   end
 
   def has_search_navbar?
-    !has_order_metatag? && pool_id.blank? && favgroup_id.blank?
+    !query.has_metatag?(:order, :ordfav, :ordpool) && pool_id.blank? && favgroup_id.blank?
   end
 
-  def has_order_metatag?
-    PostQueryBuilder.new(search).has_metatag?(:order, :ordfav, :ordpool)
+  def pool_id
+    @pool_id ||= query.find_metatag(:pool, :ordpool)&.to_i
   end
 
-  memoize :pools, :favgroups
+  def favgroup_id
+    @favgroup_id ||= query.find_metatag(:favgroup, :ordfavgroup)&.to_i
+  end
+
+  def query
+    @query ||= PostQueryBuilder.new(search)
+  end
 end