feat: Forward generics to custom_generic interface

[jawoznia]

part of #263

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Comparison is base (7ac645e) 87.25% compared to head (52eccee) 87.29%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## feat/generics_forwarding #265 +/- ## ============================================================ + Coverage 87.25% 87.29% +0.04% ============================================================ Files 25 25 Lines 1812 1811 -1 ============================================================ Hits 1581 1581 + Misses 231 230 -1 ```

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