Add character model with spec
Move shared_examples for user_controler inside user_controller
Add routes for character CRUD
Add serializer for character
Add create action for character
Character model now have index and reference to User
Bound character and user model
Add character factory
On creating character it bound it to current_user
Small refactor of shared examples
Add update action with spec to character controller
Build specs to user shared_expaplse for unprocessable entities
Add delete action for Character controller
Handle bad request in Character controller