Working on adding mutex support to model routes

Need to add a new field to the User model: space;
Spaces:
1. User - this will cause the model data routes to check the mutex meta
options on the model def when serving data apis;
2. Administrator - this will skip the mutex check;
Note that roles are only defining groups of api access privileges, they
can not protect user's data from each other when they are assigned the
same role. That's why we need a mutex setting on the models and spaces
on the user record to distinguish ways of applying the roles.