v0.5.0

Added

• tfrs.experimental.models.Ranking, an experimental pre-built model for
  ranking tasks. Can be used as DLRM like model with Dot Product feature
  interaction or DCN like model with Cross layer.

Changed

• Fixed the bug in tfrs.layers.loss.SamplingProbablityCorrection that logits
  should subtract the log of item probability.
• tfrs.experimental.optimizers.CompositeOptimizer: an optimizer that
  composes multiple individual optimizers which can be applied to different
  subsets of the model's variables.
• tfrs.layers.dcn.Cross and DotInteraction layers have been moved to
  tfrs.layers.feature_interaction package.