added swagger documentation to User API
moved controller and model documentation to external resources
created Gadget documentation
added additional information to UsersControllerDocumentation and GadgetControllerDocumentation
nesting all routes into /api
refactored Response Header and Body classes after finding some bugs documenting
updating UsersController with new syntax from Response::Body and Response::Header
documenting response messages for UserControllerDocumentation
added leftover Response::Body and Response::Header classes to project
adjusted Applicatio's Controlelrs with new syntax from Response::Body and Response::Header
fixed uniqueness of Checkpoint.sent_at
removed top level constant call
created swagger documentation for Checkpoint and CheckpointsController
included response_message codes for Gadget and User Controller documentations
including  to Models and Controllers
added produces and consumes key to controllers
removed trivial response http status codes
added produces and consumes to leftover controlelrs
fixed resourcePath for controllers
fixed api entry point documentation