:art: [#165] changed expand snake_case query params to camelCase

[bart-maykin]

Fixes #165

• Changed the query param values for the expand from snake_case to camelCase
• added snake_case to camelCase converter
• added camelCase to snake_case converter

[codecov-commenter]

Codecov Report

Attention: 2 lines in your changes are missing coverage. Please review.

Comparison is base (d05ccab) 96.57% compared to head (4626b9d) 96.55%.

Files	Patch %	Lines
src/openklant/components/utils/expansion.py	81.81%	2 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #166 +/- ## ========================================== - Coverage 96.57% 96.55% -0.03% ========================================== Files 124 126 +2 Lines 5584 5609 +25 ========================================== + Hits 5393 5416 +23 - Misses 191 193 +2 ```

:umbrella: View full report in Codecov by Sentry.
:loudspeaker: Have feedback on the report? Share it here.