(WIP) Prepare release 4.0.0

[stevenbal]

Placeholder to keep track of what needs to be removed/changed in this major release

• Rename LOG_REQUESTS to `LOG_OUTGOING_REQUESTS (change in OAF? or override locally? https://github.com/maykinmedia/open-api-framework/blob/f54907d65adfaa5dd6fd2bdaa634bbacb8b457d0/open_api_framework/conf/base.py#L552)
• Remove deprecated views for OpenAPI specs (#2189)
• Squash migrations (?)
• See if any upgrade check constraints need to be added
• Remove django.contrib.sites
• data_icontains simplify to use _icontains and add separate regex search query param?
• Potential changes to setup config for objecttypen?
• use new exception_handler from commonground-api-common (which updates error format to be application/problem+json compliant)
• only allow local objecttypes
• changes to setupconfig for objecttypes -> service and use_fields and fields removed (should we remove the step altogether?)
• TODO check more deprecations and XXX: ... comments

Release checklist

• Resolve release blockers
  • ...
• Upgrade open-api-framework to latest version
• Check security tab and upgrade packages to fix vulnerabilities
• Check translations
• Bump API version number (if applicable)
  • Version bump
  • Regenerate API spec
  • Update READMEs with release dates + links
• Bump version number with bin/bump-my-version.sh bump <major|minor|patch>
• Update changelog
• Check the impact of this release on the Helm charts and make issues for this in https://github.com/maykinmedia/charts if needed, e.g.
  • New environment variables were added
  • New setup configuration steps or changes to format
  • New containers required
  • ...