* INTERNAL:
* Initialize a ManyToOneMapping.
*/
protected ObjectReferenceMapping initManyToOneMapping() {
// Allow for different descriptor types (EIS) to create different mapping types.
ObjectReferenceMapping mapping = getDescriptor().getClassDescriptor().newManyToOneMapping();
processRelationshipMapping(mapping);
mapping.setIsOptional(isOptional());
mapping.setDerivesId(derivesId());
// Process the indirection.
processIndirection(mapping);
// Process a @ReturnInsert and @ReturnUpdate (to log a warning message)