repo-sqale: added ResultListRowTransformer#finishTransformation

Method is default and empty, so the interface is still "SAM" (single
abstract method) interface.
Method finishTransformation() is called after all the rows were
transformed and it can be extremely useful if some data were collected
during the transformation.
Example: Previously, if parent object for container was needed, it was
obtained immediately (cache map for repeated parents could be used,
of course) which meant potentially up to N queries (by OID, sure, which
is fast, but you should still shudder when you hear infamous N+1).
Now you can just collect all the distinct OID and then loaded in one
SELECT ... WHERE oid IN (...) query. Cool, isn't it?

repo/repo-sqlbase/src/main/java/com/evolveum/midpoint/repo/sqlbase/SqlQueryContext.java

@@ -458,13 +458,21 @@ public void processOptions(Collection<SelectorOptions<GetOperationOptions>> opti
     /**
      * Transforms result page with (bean + extension columns) tuple to schema type.
      * JDBC session is provided as it may be needed for additional fetches.
+     * Instead of calling some transformation method row-by-row, transformer object is provided
+     * by the table mapper - which allows for potentially stateful processing.
+     * For example, row-by-row transformation can collect information for some additional processing
+     * which can be executed by implementing {@link ResultListRowTransformer#finishTransformation()}.
      */
     public PageOf<S> transformToSchemaType(PageOf<Tuple> result, JdbcSession jdbcSession)
             throws SchemaException, QueryException {
         try {
             ResultListRowTransformer<S, Q, R> rowTransformer =
                     entityPathMapping.createRowTransformer(this, jdbcSession);
-            return result.map(row -> rowTransformer.transform(row, root(), options));
+
+            PageOf<S> transformedResult = result.map(row -> rowTransformer.transform(row, root(), options));
+            rowTransformer.finishTransformation();
+
+            return transformedResult;
         } catch (RepositoryMappingException e) {
             Throwable cause = e.getCause();
             if (cause instanceof SchemaException) {

repo/repo-sqlbase/src/main/java/com/evolveum/midpoint/repo/sqlbase/mapping/ResultListRowTransformer.java

@@ -27,4 +27,12 @@ public interface ResultListRowTransformer<S, Q extends FlexibleRelationalPathBas
 
     S transform(Tuple rowTuple, Q entityPath,
             Collection<SelectorOptions<GetOperationOptions>> options);
+
+    /**
+     * This method is called after all the rows were transformed and allows for additional
+     * final shake-up for more complex stateful transformations.
+     */
+    default void finishTransformation() {
+        // nothing by default
+    }
 }