### What
This PR updates the `create` access control functions in the
`multi-tenant` example to ensure that any `tenant` specified in a create
request matches a tenant the user has admin access to.
### Why
Previously, while the admin panel UI restricted the tenant selection, it
was still possible to bypass this by making a request directly to the
API with a different `tenant`. This allowed users to create documents
under tenants they shouldn't have access to.
### How
The `access` functions on the `users` and `pages` collections now
explicitly check whether the tenant(s) in the request are included in
the user's tenant permissions. If not, access is denied by returning
`false`.
**Fixes: CMS2-Q225-03**
50029532aa