Multitenancy without CurrentTenantIdentifierResolver

[DavideD]

Fixes #764

@gavinking shouldn't also be possible for a user to set the tenant for the stateless session?

[gavinking]

Huh, I don't get it: why to SessionFactorys have tenant ids? That doesn't seem to make sense.

shouldn't also be possible for a user to set the tenant for the stateless session?

Sure, it's easy to add.

[DavideD]

I think it's because ORM uses the following approach for the creation of the session with a tenant:

ormFactory.withOptions().tenantIdentifier( "tenantId" ).openSession()

[gavinking]

Oh, I see, Ok, fine.