Feature/121 expand

[bart-maykin]

fixes #121

added digitale_adressen field for betrokkenen to enable expand on klantcontact endpoint.

added expand for:

• Klantcontact
  • betrokkene
  • betrokkene.partij
  • betrokkene.digitaaladres
  • actor
  • internetaak
  • onderwerpobject
  • bijlage
• Partij
  • digitaaladres
  • betrokkene
  • betrokkene.klantcontact
  • betrokkene.klantcontact.actor

[codecov-commenter]

Codecov Report

Attention: 38 lines in your changes are missing coverage. Please review.

Comparison is base (2bd1e94) 96.98% compared to head (1878dae) 96.63%.

Files	Patch %	Lines
src/openklant/components/utils/inspectors.py	37.50%	20 Missing :warning:
src/openklant/components/utils/expansion.py	92.15%	12 Missing :warning:
...mponents/klantinteracties/models/klantcontacten.py	57.14%	3 Missing :warning:
src/openklant/components/utils/camilize.py	90.90%	3 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #127 +/- ## ========================================== - Coverage 96.98% 96.63% -0.36% ========================================== Files 177 183 +6 Lines 7366 7697 +331 ========================================== + Hits 7144 7438 +294 - Misses 222 259 +37 ```

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