pools: store post_ids as array instead of string (fix #3979)

test/functional/pool_elements_controller_test.rb

@@ -21,14 +21,14 @@ class PoolElementsControllerTest < ActionDispatch::IntegrationTest
       should "add a post to a pool" do
         post_auth pool_element_path, @user, params: {:pool_id => @pool.id, :post_id => @post.id, :format => "json"}
         @pool.reload
-        assert_equal([@post.id], @pool.post_id_array)
+        assert_equal([@post.id], @pool.post_ids)
       end
 
       should "add a post to a pool once and only once" do
         as_user { @pool.add!(@post) }
         post_auth pool_element_path, @user, params: {:pool_id => @pool.id, :post_id => @post.id, :format => "json"}
         @pool.reload
-        assert_equal([@post.id], @pool.post_id_array)
+        assert_equal([@post.id], @pool.post_ids)
       end
     end
 
@@ -40,7 +40,7 @@ class PoolElementsControllerTest < ActionDispatch::IntegrationTest
       should "remove a post from a pool" do
         delete_auth pool_element_path, @user, params: {:pool_id => @pool.id, :post_id => @post.id, :format => "json"}
         @pool.reload
-        assert_equal([], @pool.post_id_array)
+        assert_equal([], @pool.post_ids)
       end
 
       should "do nothing if the post is not a member of the pool" do
@@ -50,7 +50,7 @@ class PoolElementsControllerTest < ActionDispatch::IntegrationTest
         end
         delete_auth pool_element_path, @user, params: {:pool_id => @pool.id, :post_id => @post.id, :format => "json"}
         @pool.reload
-        assert_equal([], @pool.post_id_array)
+        assert_equal([], @pool.post_ids)
       end
     end
   end