This adds support for multi project tokens to be created. Backward compatibility is handled at 3 different layers here:
- The API is made backwards compatible though a permissive data type that accepts either a project?: string or projects?: string[] property, validation is done through JOI here, which ensures that projects and project are not set together. In the case of neither, this defaults to the previous default of ALL_PROJECTS
- The service layer method to handle adding tokens has been made tolerant to either of the above case and has been deprecated, a new method supporting only the new structure of using projects has been added
- Existing compatibility for consumers of Unleash as a library should not be affected either, the ApiUser constructor is now tolerant to the the first input and will internally map to the new cleaned structure
