fix: add To header to emailsender emails

[johannes94]

Description

This PR fixes emailsender to set the "To" header of emails sent. The header is explicitly not set by the acscsEmail integration to allow emailsender to append. But that part was forgotten during initial implementation.

This led to emails being send but email clients would show an empty To header.

Checklist (Definition of Done)

• Unit and integration tests added
• Added test description under Test manual
• Documentation added if necessary (i.e. changes to dev setup, test execution, ...)
• CI and all relevant tests are passing
• Add the ticket number to the PR title if available, i.e. ROX-12345: ...
• Discussed security and business related topics privately. Will move any security and business related topics that arise to private communication channel.
• Add secret to app-interface Vault or Secrets Manager if necessary
• RDS changes were e2e tested manually
• Check AWS limits are reasonable for changes provisioning new resources
• (If applicable) Changes to the dp-terraform Helm values have been reflected in the addon on integration environment

Test manual

make db/teardown db/setup

#Login to ocm and AWS dev account before running this

make run/emailsender

curl localhost:8080/api/v1/acscsemail -v -XPOST \
-H "Content-Type: application/json" \
-H "Authorization: Bearer $(ocm token)" \
--data-raw '{"to":["[email protected]"], "rawMessage":"dGVzdCBtZXNzYWdlIGNvbnRlbnQ="}'

# Verify
# 1. Status code is successful and you receive the email
# 2. From and To headers are set like expected

[kurlov]

🎉

[openshift-ci]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: johannes94, kurlov

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[johannes94]

/retest