[#1566] Add email registration to case detail contact form

[vaszig]

FYI, currently we have the contact form in the case detail view but we only support sending a question via the api configuration. With this task we want to add the email configuration as well.

It will be easier to review this if you take a look at https://github.com/maykinmedia/open-inwoner/blob/develop/src/open_inwoner/openklant/views/contactform.py, where Bart had already implemented this for the basic contact form page.

[codecov-commenter]

Codecov Report

Merging #700 (65dac2a) into develop (087347a) will increase coverage by 0.02%.
The diff coverage is 96.45%.

@@             Coverage Diff             @@
##           develop     #700      +/-   ##
===========================================
+ Coverage    96.17%   96.20%   +0.02%     
===========================================
  Files          636      639       +3     
  Lines        22683    22887     +204     
===========================================
+ Hits         21816    22019     +203     
- Misses         867      868       +1     

Impacted Files	Coverage Δ
src/open_inwoner/configurations/admin.py	100.00% <ø> (ø)
src/open_inwoner/utils/tests/helpers.py	89.16% <66.66%> (-1.83%)	⬇️
src/open_inwoner/cms/cases/views/status.py	88.84% <83.87%> (-0.35%)	⬇️
src/open_inwoner/cms/cases/tests/test_htmx.py	57.93% <87.50%> (+0.21%)	⬆️
src/open_inwoner/utils/tests/playwright.py	76.81% <91.66%> (-1.92%)	⬇️
src/open_inwoner/accounts/forms.py	97.80% <100.00%> (+0.04%)	⬆️
...c/open_inwoner/accounts/tests/test_action_views.py	88.78% <100.00%> (ø)
src/open_inwoner/accounts/tests/test_inbox_page.py	94.94% <100.00%> (-0.03%)	⬇️
src/open_inwoner/accounts/tests/test_logging.py	100.00% <100.00%> (ø)
.../open_inwoner/accounts/tests/test_profile_views.py	100.00% <100.00%> (ø)
... and 8 more

... and 1 file with indirect coverage changes

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[alextreme]

Looks good to me, this is in line with how the general contactform works

[pi-sigma]

Looking good (the suggested change is cosmetic).