Capture authentication context data

[sergei-maertens]

Part of #3623

Currently the "machtigen" context data is stored as a simple JSON field, which doesn't capture everything that should be captured, and the shape is also not well documented. For this, some changes are needed:

• [x] Patch our OIDC library so that we can map properties with . characters too
• [x] Release new version of mozilla-django-oidc-db
• [x] Investigate removing the "django-solo" nature of the OIDC config model(s) (and do more with JSONField for config)
• [ ] Establish structure of authentication context in models (authentication.AuthInfo)
  • Record/translate means (digid/eherkenning/...)
  • Record LOA
  • Record authorizee
  • Record representee
  • Record mandate context (service(s), role...)
• [ ] Implement AuthInfo.to_auth_context_data() method and validate that against the JSON schema's (for robustness)
• [ ] Update static variables to read from the appropriate place(s)
• [ ] Update prefill to read from the appropriate place(s)