PurchaseWindowDecorator: Convert to new action links interface

Also add a new method `AF83::Decorator.define_instance_method`. Thanks
to Johan for suggesting that and walking me through writing it. This new
method allows us to define methods on the instance decorator. We need
this to preserve the `#bounding_dates` method that was defined in
`PurchaseWindowDecorator`.

Refs #5586

1 files changed, 4 insertions, 0 deletions

diff --git a/lib/af83/decorator.rb b/lib/af83/decorator.rb
index e83e03e0f..1b9574053 100644
--- a/lib/af83/decorator.rb
+++ b/lib/af83/decorator.rb
@@ -28,6 +28,10 @@ class AF83::Decorator < ModelDecorator
     end
   end
 
+  def self.define_instance_method method_name, &block
+    instance_decorator.send(:define_method, method_name, &block)
+  end
+
   class ActionLinks
     attr_reader :options