Fix #3696: API: handle boolean params consistently

* Use ApplicationRecord#attribute_matches to handle boolean attributes
  consistently in search methods.

* Add support for searching various boolean attributes that previously
  weren't supported.

app/models/pool.rb

@@ -70,23 +70,14 @@ class Pool < ApplicationRecord
         q = q.where(creator_id: params[:creator_id].split(",").map(&:to_i))
       end
 
-      if params[:is_active] == "true"
-        q = q.where("pools.is_active = true")
-      elsif params[:is_active] == "false"
-        q = q.where("pools.is_active = false")
-      end
-
       if params[:category] == "series"
         q = q.series
       elsif params[:category] == "collection"
         q = q.collection
       end
 
-      if params[:is_deleted] == "true"
-        q = q.deleted
-      else
-        q = q.undeleted
-      end
+      q = q.attribute_matches(:is_active, params[:is_active])
+      q = q.attribute_matches(:is_deleted, params[:is_deleted])
 
       params[:order] ||= params.delete(:sort)
       case params[:order]