Database-isolation strategy: a discriminant string, or a custom ITenantIsolationStrategy instance. Default: 'column-per-tenant'.

A strategy NAMES the isolation an ITenantDataStore is expected to implement; it does not by itself create schemas or databases. The shipped MemoryTenantDataStore uses the strategy's label as a partition-map key, so all three kinds isolate correctly on it — but no shipped adapter is told the strategy. A register() warning fires when a non-'column-per-tenant' strategy is selected with no dataStore.