Feature/46 use django simple certmanager library

[Ewen-Lgy]

Fixes #46

Extracting the certficate manager to a standalone library

[codecov]

Codecov Report

Merging #47 (f5ada3c) into main (6cd56ba) will decrease coverage by 5.99%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main      #47      +/-   ##
==========================================
- Coverage   51.71%   45.72%   -6.00%     
==========================================
  Files          40       37       -3     
  Lines        1512     1358     -154     
  Branches      249      223      -26     
==========================================
- Hits          782      621     -161     
- Misses        689      700      +11     
+ Partials       41       37       -4     

Impacted Files	Coverage Δ
zgw_consumers/admin.py	76.92% <ø> (-11.76%)	⬇️
zgw_consumers/constants.py	100.00% <ø> (ø)
zgw_consumers/utils.py	42.10% <ø> (-7.90%)	⬇️
zgw_consumers/models/certificates.py	100.00% <100.00%> (+1.75%)	⬆️
zgw_consumers/models/services.py	76.42% <100.00%> (-4.88%)	⬇️
zgw_consumers/client.py	64.70% <0.00%> (-15.69%)	⬇️

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[sergei-maertens]

Can you also update the translation files, there should be some that are gone now.

``django-admin makemessages -l nl`

[sergei-maertens]

Tested the forwards and reverse (data) migration on Open Forms project and it works as expected 👍