DatabaseBlockStore can be used to insert Blocks into foreign databases. In order to make it a proper cross-wiki store a DatabaseBlockStoreFactory should be added and injected in order to get the correct DatabaseBlockStore when inserting a block into the database.
A LBFactory should be injected into DatabaseBlockStoreFactory which then injects the correct LoadBalancer into a DatabaseBlockStore.
The new DatabaseBlockStoreFactory should then be injected into BlockUser instead of DatabaseBlockStore. The block related methods should then get a wiki parameter, which is then used to fetch the correct store.