Warpgate: Missing authorization check on `PUT /users/:id/roles/:role_id` allows any admin to bypass the `AccessRolesAssign` permission boundary

Warpgate is an open source SSH, HTTPS and MySQL bastion host for Linux. Prior to 0.28.4, PUT /@warpgate/admin/api/users/:id/roles/:role_id reaches api_update_user_role in warpgate-admin/src/api/users.rs through AdminContext but does not require AdminPermission::AccessRolesAssign. A limited administrator with any permission can update expires_at on an existing UserRoleAssignment and clear revoked_at, extending an expiring grant or reinstating a revoked grant. The endpoint cannot create a role assignment that never existed because it returns not found without a matching user and role pair. This issue is fixed in version 0.28.4.