Add method find_by_slug_or_id to Sluggable module

Make it easier to find by slug or id for sluggable models. Will return
nil if resource is not found.

app/controllers/budgets/executions_controller.rb

@@ -25,7 +25,7 @@ module Budgets
       end
 
       def load_budget
-        @budget = Budget.find_by(slug: params[:budget_id]) || Budget.find_by(id: params[:budgetid])
+        @budget = Budget.find_by_slug_or_id params[:budget_id]
       end
 
       def investments_by_heading_ordered_alphabetically

app/models/concerns/sluggable.rb

@@ -3,6 +3,10 @@ module Sluggable
 
   included do
     before_validation :generate_slug, if: :generate_slug?
+
+    def self.find_by_slug_or_id(slug_or_id)
+      find_by_slug(slug_or_id) || find_by_id(slug_or_id)
+    end
   end
 
   def generate_slug