fix: recursive input params in `union_input` transformer

[ouertani]

Summary:
Briefly describe the changes made in this PR.

Issue Reference(s):
Fixes #... (Replace "..." with the issue number)

Build & Testing:

• [X] I ran cargo test successfully.
• [X] I have run ./lint.sh --mode=fix to fix all linting issues raised by ./lint.sh --mode=check.

Checklist:

• [X] I have added relevant unit & integration tests.
• [ ] I have updated the documentation accordingly.
• [ ] I have performed a self-review of my code.
• [ ] PR follows the naming convention of <type>(<optional scope>): <title>

[codecov[bot]]

Codecov Report

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

Project coverage is 86.04%. Comparing base (1f74665) to head (ca1fc19).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #2337 +/- ## ======================================= Coverage 86.04% 86.04% ======================================= Files 235 235 Lines 22515 22526 +11 ======================================= + Hits 19372 19383 +11 Misses 3143 3143 ```

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