default Cleanable getCleanableFor(Connection conn) {
        return () -> this.closeConnection(conn);
    }
Returns a {@link Cleanable} that will close the connection and release all necessary resources.
Like {@link Connection#close()}, the Cleanable should no-op if called more than once.

@param conn A {@link Connection} object.
@return A {@link Cleanable} instance. Calling the {@link Cleanable#close()} method will close the connection and release all resources.
core/src/main/java/org/jdbi/v3/core/ConnectionFactory.java