Tenant (root entity)
 |- list of references to User root entities

User (root entity)
 |- list of TenantRoles by tenant id
    |- list of Role root entities

Role (root entity)


example:

Tenant(Bar)
 |- User(Foo)
 |- User(Fab)

Tenant(Baz)
 |- User(Foo)

User(Foo)
 |- TenantRole(Bar)
    |- Role(Admin)
 |- TenantRole(Baz)
    |- Role(Admin)

User(Fab)
 |- TenantRole(Bar)
    |- Role(Nobody)


Role(Admin)
Roel(Nobody)