quick hack to optimize finding max valid fa_id

sorbet/rbi/shims/aux.rbi

@@ -0,0 +1,9 @@
+# typed: strict
+
+class DomainPostsFaAux < ActiveRecord::Base
+  extend T::Sig
+
+  sig { returns(T.nilable(Integer)) }
+  def fa_id
+  end
+end