ENG-3299: Add CorrespondenceMetadata model and table

[JadeCara]

Ticket ENG-3299

Dependency: Requires #7866 to be merged first (stacked PR)

Description Of Changes

PR 2 of 2 for ENG-3299. Creates the CorrespondenceMetadata table with a 1:1 relationship to Comment for delivery tracking and email threading.

Table fields:

• comment_id — FK to comment.id, UNIQUE (1:1), CASCADE delete
• message_id — UNIQUE, indexed (idempotency key for deduplication)
• in_reply_to — threading reference to parent message
• reply_to_address — indexed for inbound routing
• delivery_status — varchar with default pending (values: pending/sent/delivered/bounced/failed)
• delivered_at, bounce_reason, sender_email, recipient_email

Design decision: delivery_status uses varchar (not a PG enum) to avoid cross-migration enum type dependencies. Validation happens at the Python model layer via CorrespondenceDeliveryStatus enum.

Code Changes

• src/fides/api/models/comment.py — Added CorrespondenceMetadata model with 1:1 relationship to Comment
• src/fides/api/db/base.py — Registered CorrespondenceMetadata for Alembic discovery
• New migration: creates correspondence_metadata table with indexes and constraints

Steps to Confirm

1. Run alembic upgrade head — verify table created
2. Run alembic downgrade -1 then alembic upgrade head — verify full cycle
3. Verify table schema: \d correspondence_metadata shows all columns, UNIQUE on comment_id and message_id, FK to comment.id with CASCADE
4. Run pytest tests/ctl/models/test_comment.py — all pass

Pre-Merge Checklist

• Issue requirements met
• All CI pipelines succeeded
• CHANGELOG.md updated
  • Add a db-migration This indicates that a change includes a database migration label to the entry if your change includes a DB migration
  • Add a high-risk This issue suggests changes that have a high-probability of breaking existing code label to the entry if your change includes a high-risk change
  • Updates unreleased work already in Changelog, no new entry necessary
• UX feedback:
  • All UX related changes have been reviewed by a designer
  • No UX review needed
• Followup issues:
  • Followup issues created
  • No followup issues
• Database migrations:
  • Ensure that your downrev is up to date with the latest revision on main
  • Ensure that your downgrade() migration is correct and works
    • If a downgrade migration is not possible for this change, please call this out in the PR description!
  • No migrations
• Documentation:
  • Documentation complete, PR opened in fidesdocs
  • Documentation issue created in fidesdocs
  • If there are any new client scopes created as part of the pull request, remember to update public-facing documentation that references our scope registry
  • No documentation updates required

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2 Skipped Deployments

Project	Deployment	Actions	Updated (UTC)
fides-plus-nightly	Ignored	Preview	Apr 9, 2026 10:58pm
fides-privacy-center	Ignored		Apr 9, 2026 10:58pm

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 85.09%. Comparing base (e5c7f63) to head (bb8a2d7).
⚠️ Report is 2 commits behind head on ENG-3299/enums-scopes-encryption.

Additional details and impacted files

@@                        Coverage Diff                        @@
##           ENG-3299/enums-scopes-encryption    #7867   +/-   ##
=================================================================
  Coverage                             85.08%   85.09%           
=================================================================
  Files                                   627      628    +1     
  Lines                                 40799    40821   +22     
  Branches                               4742     4742           
=================================================================
+ Hits                                  34714    34736   +22     
  Misses                                 5017     5017           
  Partials                               1068     1068           

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