Make Test[<Definition>] just return that Definition instance

Author: ahx

lib/openapi_first/registry.rb

@@ -30,6 +30,8 @@ def register(path_or_definition, as: :default)
     end
 
     def [](api)
+      return api if api.is_a?(Definition)
+
       definitions.fetch(api) do
         option = api == :default ? '' : ", as: #{api.inspect}"
         raise(NotRegisteredError,

spec/test_spec.rb

@@ -389,6 +389,11 @@ def call(_env)
         described_class[:mine]
       end.to raise_error(OpenapiFirst::NotRegisteredError)
     end
+
+    it 'just returns a Definition' do
+      oad = definition
+      expect(described_class[oad]).to be(oad)
+    end
   end
 
   describe 'handling invalid requests' do