This class should contain a NamespaceString and a tenantID. The tenantID should be optional, and should only be required if the server parameter multitenancySupport is enabled and the feature flag featureFlagRequireTenantID is on. The string representation of this type should be tenantID_dbName.collName as it is today.

When constructing a TenantNamespace from a string, if multitenancySupport is enabled the tenantID should be parsed separately from the db name. If it is not enabled, it will be parsed as a part of the db name (and the tenantID will be empty).