PDJB-1260: Send registration confirmation email for organisation landlords

[Bill-Haigh]

Ticket number

PDJB-1260

Goal of change

Organisation landlords received no confirmation email on completing registration.

Description of main change(s)

• Sends a confirmation email when an organisation landlord completes registration, with organisation-specific copy ("You have registered [organisation name] as a landlord")
• Adds the ORGANISATIONAL_LANDLORD_REGISTRATION_CONFIRMATION_EMAIL template, including its Notify template IDs
• Narrows the existing individual-landlord email helper to take an IndividualLandlord, removing its runtime type check
• Extends the organisation journey integration test to submit check your answers and assert the email is sent

Anything you'd like to highlight to the reviewer?

• The email goes to the registrant's email address. This branch is rebased onto PDJB-1282, which added the registrant email step and made OrgLandlordRegistrationCyaStepConfig populate organisationRegistrantEmail for real. The second commit switches the recipient from the organisation address to the registrant's and removes the // TODO: PDJB-1282 that was tracking it. The integration test submits a registrant email that differs from the organisation email, so the assertion proves which one is used.
• Submitting check your answers still renders an error page for org landlords. RegisterLandlordController.getConfirmation resolves the landlord via retrieveLandlordByBaseUserId, which only returns IndividualLandlords. Pre-existing and out of scope here, so the integration test asserts the email and carries a // TODO: PDJB-1392 where the confirmation page assertion belongs.
• Naming. Following review, the identifiers this PR introduces use Organisational.... The pre-existing OrganisationLandlord entity and the ORGANISATION_LANDLORD_REGISTRATION feature flag are deliberately untouched - a separate PR will rename those.
• The template was verified against the live Notify API via NotifyEmailTemplateTests, so the source-controlled markdown matches Notify exactly.

Pre-release steps

NotifyEmailTemplateTests only checks the template ID for the Notify service its API key belongs to (non-prod, test_id), and is skipped when EMAILNOTIFICATIONS_APIKEY is unset - so CI does not cover any of the below.

• test & nft - check the Notify template ID for ORGANISATIONAL_LANDLORD_REGISTRATION_CONFIRMATION_EMAIL is correct
• prod - check the Notify template ID is correct
• prod - check the email template matches pre-prod

Checklist

• Unit tests for new logic (e.g. new service methods) have been added
• New email templates have been added to /src/main/kotlin/resources/emails/emailTemplates.json
• Test suite has been run in full locally and is passing
• Branch has been rebased onto main and run locally, with everything working as expected (both for your new feature
  and any related functionality)
• TODO comments referencing this JIRA ticket have been searched for and removed - two TODOs referencing future
  tickets remain: PDJB-1274 (reassess the recipient address and name once there is a general way to email a landlord)
  and PDJB-1392 (assert the confirmation page in the integration test)
• Any special release instructions (e.g. the database will need resetting, emails to be added/removed) have been to the relevant release
  ticket on the Jira board, referencing your ticket number
• QA instructions have been added to the ticket (particularly if this is the last PR required to complete the ticket)
• This feature is behind a feature flag. I've checked that there will be no change in function if the feature flag is disabled

[danielledias-MT]

Approved with minor suggestions

[samyou-softwire]

LGTM, couple comments on namings/todos

[samyou-softwire]

if we're adding new emails, we should have a pre release step to

• on test/nft & prod to check the notify email template IDs are correct
• on prod the email template matches pre-prod

since our automated testing won't cover this

[Travis-Softwire]

Do our notify tests not check prod notify? (Genuine question - I know they check our lower env notify)