Move confirmation email reference generation to job runtime

[theseanything]

Move confirmation email reference creation from EmailConfirmationInput request-time handling into SendConfirmationEmailJob, so the Notify reference is generated when the job executes only when we need it.

Removes a lot of unnecessary code and makes EmailConfirmationInput model simpler.

We don't need to log the notify_response_id at request time, as request will not fail due a notify error - so little use to correlate them.

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[github-actions]

🎉 A review copy of this PR has been deployed! It is made of up two components

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2. A production copy of forms-admin

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[DavidBiddle]

We use this hidden reference in the end-to-end tests: https://github.com/alphagov/forms-e2e-tests/blob/5af8577d3291d7490634340bcd616badfda10e72/spec/support/feature_helpers.rb#L385

I think without this we'll either need to find another way of knowing which reference to look for in the Notify API or another way of checking the Notify content

[theseanything]

ah good catch! I'll take a look at decoupling the e2e tests