Detect more problems and add them to the email digest

[sergei-maertens]

Target audience: functional administrators Goal: avoid things breaking silently (things will break)

Things that go wrong during runtime

• [x] All submissions with failed registration status (or a handy admin link to filter those)

  • check TimelineLog from past 24 hours
  • aggregate on form title/name + number of failed submissions + clickable link to submissions admin with preconfigured filters, e.g. /admin/submissions/submission?form=123&state=failed&from=24hAgo
  • (add submission filter for 'past 24 hours')
  • when was first & last failure in the past 24 hours
  • example text in email: Aanvraag subsidie registratie gefaald: 3 times between 14:03 and 15:24 in the past 24 hours

• [x] Log failures (e.g. from prefill) (e.g. create log record that we can filter on) etc. & include how many failed each day (and aggregate problem)

See also #3999 which may overlap for (Prometheus) metrics.

• The page to view these relevant log records should include/display sufficient context, like which form(s) are affected, timestamps..., type of error (maybe)?
• Pointers to where people can look to investigate
  • logs
  • tip to enable request logging?

Things that can go wrong/cause support overhead because of broken configuration

• [x] If addressNL components are used in (active) forms, then the BRK client must be configured properly. If this is not the case, include it as a problem that needs attention. (from github PR review comment: )
• [x] Deriving street/city from postal code/number without configuring the BAG API
• [x] Are forms still valid or not?
  • Registration backend configuration
  • Broken logic rules (fields that no longer exist)
  • ~~Deprecated components~~ (in screen warning better?)
• [x] (zgw consumers) services / configuration overview -> run test periodically & include result?
  • certificate checks (inspecting error responses + educated guesses/suggestions)
  • warn of certificate expiries (when <= 2 weeks to go?)
  • host connection / credentials
  • configuration complete or not