Ensure surveyor always created when user created

[lfilmeyer]

I added the /admin/users endpoint which allows for the creation of an admin without surveyor data. However, we should always create a surveyor object when we create a user so that the user will show up on the Users page (which actually calls the GET /surveyors index). In a perfect world, the users and surveyors objects would probably be merged into 1 model, but that's a non-trivial amount of work to cleanup.

On the backend, we should validate the presence of surveyor on a user. It's currently a low priority issue because the frontend requires surveyor attributes, so in practice we are always creating surveyors with users.