1.9.0
FIX metadata routing in `learning_curve` and related module tests (#34039)
MNT Switch to absolute imports enforced by `ruff` (#31847)
FIX: HTML representation with nested meta-estimator (#33889)
DOC/MNT Little clean up around the splitting docs and error message (#33091)
FEA Callbacks API (#33322)
FIX: StratifiedGroupKFold errors when n_splits > n_groups (#33176)