prepare migration of permission to roles
this simplify drastically database (permission are now simply defined in code)
and will permit reuse of the same ReBAC engine to define owners of drives
mapping:
```
Role::Viewer => &[Permission::Read],
Role::Commenter => &[Permission::Read, Permission::Comment],
Role::Contributor => &[Permission::Read, Permission::Create],
Role::Editor => &[
Permission::Read,
Permission::Comment,
Permission::Create,
Permission::Update,
],
Role::Owner => &[
Permission::Read,
Permission::Comment,
Permission::Create,
Permission::Update,
Permission::Share,
Permission::Delete,
Permission::Manage,
],
```
Edouard Vanbelle