- revise data model to new version (without project)
- adapt database test to new data model
- use separate folder for all endpoint defs and functions to avoid circular deps
- add all API endpoints and skeletons for their implementation
- Moves `POST /users` to the users endpoint group where
authentication is required
- Renames userLogin to loginRequest
- Adds userMethods.go source file to the package user
- Adds type User in the user package which just wrapps the type
common.User so methods can be added to the type
- Adds prototypes of methods for setting/validating password and
updating type User's data
