code: public <T extends ChatStore> ChatConfig store(StoreFactory<T> builder) {
          this.storeFactory = builder.asChatStoreFactory();
          return this;
      }
docs: Sets builder for {@link ChatStore} db interface that can handle single db transactions.
  
  @param builder Factory class to create {@link ChatStore}.
  @param <T> Generic type of persistance store parent class.
  @return Builder instance with new value set.