remove MultitenancyStrategy

[gavinking]

The MultitenancyStrategy enum is currently not useful.

• MultitenancyStrategy.DISCRIMINATOR is a nice idea, but it's never been implemented
• There's actually no difference at all between MultitenancyStrategy.SCHEMA and MultitenancyStrategy.DATABASE, and it's misleading to have them represented by two different enumerated values.

I believe this thing could be removed with almost no impact on users at all.

[yrodiere]

On a side note, Hibernate Search needs to determine whether multi-tenancy is enabled or not. And it needs to do so very early, basically just after Metadata creation. Currently it does so by inspecting the MultitenancyStrategy. We don't care about the exact strategy, though.

So to anyone doing this change: please leave some way to detect that :)

See https://github.com/hibernate/hibernate-search/blob/21c2f0507f761bb80d74738870bcac7f4a741c60/mapper/orm/src/main/java/org/hibernate/search/mapper/orm/mapping/impl/HibernateOrmMappingInitiator.java#L74-L79

[gavinking]

Yeah, sure, we're still going to need at least some setting to turn it on, even if it turns out to just be the MULTI_TENANT_CONNECTION_PROVIDER. And that information's still going to be available via the ConfigurationService.

[sebersole]

• MultitenancyStrategy.DISCRIMINATOR is a nice idea, but it's never been implemented

But the hope is to do it someday. I don't have a strong opinion about this atm, but it would suck to remove it and add it back later