Add transaction-level cache to lucid

[m-i-c-h-a-l]

In JPA (Hibernate, etc.), there is a transaction-level cache, also known as the L1 cache. When the same record is loaded by its ID twice within the same database transaction, the second load is served from the local cache bound to that transaction instead of being fetched from the database. This can significantly improve performance in certain scenarios.

Of course, it’s possible to implement similar behavior manually, but it usually requires adding chunks of boilerplate code. It would be great to have this feature built directly into Lucid.