feat: allow passing transient data from registration to webhook

[CaptainStandby]

Related issue(s)

Checklist

• I have read the contributing guidelines.
• I have referenced an issue containing the design document if my change
  introduces a new feature.
• I am following the
  contributing code guidelines.
• I have read the security policy.
• I confirm that this pull request does not address a security
  vulnerability. If this pull request addresses a security vulnerability, I
  confirm that I got the approval (please contact
  [email protected]) from the maintainers to push
  the changes.
• I have added tests that prove my fix is effective or that my feature
  works.
• I have added or changed the documentation.

Further Comments

[codecov]

Codecov Report

Merging #3104 (8e5a45f) into master (342bfb0) will decrease coverage by 0.20%.
The diff coverage is 100.00%.

❗ Current head 8e5a45f differs from pull request most recent head a3c28e5. Consider uploading reports for the commit a3c28e5 to get more accurate results

@@            Coverage Diff             @@
##           master    #3104      +/-   ##
==========================================
- Coverage   77.70%   77.50%   -0.20%     
==========================================
  Files         315      314       -1     
  Lines       19963    19897      -66     
==========================================
- Hits        15512    15421      -91     
- Misses       3265     3285      +20     
- Partials     1186     1191       +5     

Impacted Files	Coverage Δ
selfservice/flow/registration/flow.go	96.92% <ø> (ø)
selfservice/strategy/oidc/strategy.go	63.47% <100.00%> (+0.15%)	⬆️
selfservice/strategy/oidc/strategy_registration.go	65.40% <100.00%> (+0.44%)	⬆️
selfservice/strategy/password/registration.go	68.33% <100.00%> (+0.53%)	⬆️
selfservice/strategy/webauthn/registration.go	65.95% <100.00%> (+0.36%)	⬆️
courier/courier_dispatcher.go	43.42% <0.00%> (-25.00%)	⬇️
persistence/sql/persister_courier.go	83.33% <0.00%> (-4.77%)	⬇️
continuity/test/persistence.go

Help us with your feedback. Take ten seconds to tell us how you rate us. Have a feature suggestion? Share it here.

[zepatrik]

Nice, looks very good! I just have a few last questions.