Update return codes for aligning with API definition

src/controllers/App_domains.cpp

src/controllers/App_users.cpp

src/controllers/Apps.cpp

src/controllers/Auth.cpp

src/controllers/Base_resource.tpp

src/controllers/Classifiers.tpp

src/controllers/Domains.cpp

src/controllers/Enumerations.cpp

src/controllers/Instances.cpp

src/controllers/Languages.cpp

src/controllers/Models.cpp

src/controllers/Nothing.cpp

src/controllers/Translations.cpp

src/controllers/Trash.cpp

src/controllers/Users.cpp