(red) Write failing testModelDecorator#to_param_injector returns an
instance of ToParamInjector
(green) ModelDecorator#to_param_injector returns an instance of
ToParamInjector

- Also fixed a typo in the test
(red) Write failing test =>  ModelDecorator#version_5_uuid_setter
returns an instance of Version5UuidSetter
(green) ModelDecorator#version5_uuid_setter returns an instance of
Version5UuidSetter
Refactor ModelDecorator and Version5UuidSetter
Refactor test & code for Version5UuidSetter
Dry up tests by moving regex for uuid pattern into a macro