Feature/oi integration fixes

[Floris272]

fixes some issues with OI and other stuff.

• Originally added tinymce.HTMLFIELD to all textfields but some fields in OI do not use the CKEditorWidget and are rendered as text so the fields in OP are changed back.
• Added GeoAdminMixin to show the map in the admin after the address has been set on Location or Organisation.
• Added OpenFormSlug field to ProductType that can be set from OF when a form is generated.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 85.10%. Comparing base (c56b396) to head (aaba0ae).

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #39      +/-   ##
==========================================
+ Coverage   84.95%   85.10%   +0.14%     
==========================================
  Files          90       90              
  Lines        1987     2007      +20     
  Branches      169      173       +4     
==========================================
+ Hits         1688     1708      +20     
  Misses        269      269              
  Partials       30       30              

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[swrichards]

LGTM, een nitpick, een vraag.