Function role_access_level 

pub fn role_access_level(user_roles: &[Box<str>]) -> AccessLevel

Access level granted purely by community-role membership on a tenant-owned file. Only roles from crate::roles::ROLE_HIERARCHY count.

Membership is matched explicitly rather than by testing “the role slice is non-empty”: a [""] slice reads as “has a role” and would hand every federated stranger Read access. Second defence behind roles::parse_roles, which drops empty segments.