Using the H2Dialect, how does one retrieve auto-generated keys?

[aboisvert]

The H2Dialect doesn't support the 'returning' clause, so I'm wondering what's the recommended way to retrieve auto-generated keys? (e.g. upon insert, it's typical to retrieve a row's generated primary key such as id)

This is typically done at a low-level through JdbcStatement.getGeneratedKeys but I don't see this capability available through the scalasql abstractions.
https://h2database.com/javadoc/org/h2/jdbc/JdbcStatement.html#getGeneratedKeys--

[aboisvert]

@lihaoyi was generous enough to jump on this and implement it right away, see #8