DT-1591: Consolidate send mail methods

[rushtong]

Addresses

Partially addresses https://broadworkbench.atlassian.net/browse/DT-1591
Specifically, bullet point 2:

The EmailService methods saveEmailAndResponse and sendMessage could be further refactored now that saveEmailAndResponse is only used in one place.

Summary

This PR simplifies EmailService by combining methods. We now delegate the creation date to the database instead of passing it in via application code. Additionally, tests are updated for coverage and comprehensiveness.

---

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[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
100.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[Copilot]

Pull request overview

This PR consolidates email persistence into EmailService.sendMessage and introduces an insert-specific mail DTO so the database owns create_date assignment.

Changes:

• Adds MailMessageInsert for new email records without emailId or createDate.
• Updates MailMessageDAO.insert to populate create_date with NOW().
• Refreshes affected DAO/service tests for the new insert model and date behavior.

Reviewed changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
src/main/java/org/broadinstitute/consent/http/service/EmailService.java	Inlines send response persistence into sendMessage using MailMessageInsert.
src/main/java/org/broadinstitute/consent/http/models/mail/MailMessageInsert.java	Adds insert-only record for persisted email fields.
src/main/java/org/broadinstitute/consent/http/db/MailMessageDAO.java	Changes insert binding type and delegates create_date to the database.
src/test/java/org/broadinstitute/consent/http/service/EmailServiceTest.java	Updates and expands service tests for SendGrid responses, categories, and persistence.
src/test/java/org/broadinstitute/consent/http/db/MailMessageDAOTest.java	Updates DAO tests for MailMessageInsert and database-provided create dates.
src/test/java/org/broadinstitute/consent/http/db/UserDAOTest.java	Updates email insert test setup to use MailMessageInsert.
src/test/java/org/broadinstitute/consent/http/db/ElectionDAOTest.java	Updates reminder email insert setup to use MailMessageInsert.
src/test/java/org/broadinstitute/consent/http/db/DataAccessRequestDAOTest.java	Updates DAR email insert setup to use MailMessageInsert.