FWIW the "manual/explicit" approach suggested in the description would be plenty. No need for autodetection ias far as I'm concerned.

Also, having to indicate a context that is multi-tenant is also fine (currently I'm looking at annotating the DAOs that are multi-tenant and having the aspect processor ensure code is run before/after methods in those classes. This gives a benefit of allowing contexts where we don't want the tenancy enforced - for example when we create a new account/tenant during customer auto-registration.