[FEA] Multi-task prediction support with Next-Item-Prediction

[vivpra89]

🚀 Feature request

Current BinaryClassificationTask, RegressionTask can be used in multi-task scenario. Provide a way to include NextItem + Binary / Multiclass prediction

Motivation

There are cases where we want to predict NextItem for purchases and NextItem for Add To Carts. Those Cases arent supported currently

[vivpra89]

Transformers4Rec/tests/unit/torch/test_trainer.py

Line 505 in 30f0946

def test_trainer_with_multiple_tasks(schema_type):

This shows how to use NextItemPred with classification task.