Add remaining missing webhook email data fields (#105)

[felipefreitag]

Closes #105.

Completes EmailEventData parity with the Resend webhook payload. Field shapes verified against the server assembly (monorepo/apps/email-events-webhooks-consumer/src/utils/call-webhook.ts) and the OpenAPI spec. #112 added several fields but left these out:

New fields

• open (EmailOpenData: ipAddress, timestamp, userAgent) — set for email.opened. Mirrors EmailClickData without link. This was the most notable gap — opens are common and the payload was previously dropped.
• headers (List<EmailEventHeader>) — custom headers, present on every email event (inbound and outbound). Sent by the server as an array of {name, value}.
• received_for (EmailAddressList) — inbound email.received only.
• suppressed.reason and suppressed.diagnosticCode — the server sends {message, type, reason, diagnosticCode}; Updating webhook data fields #112 modeled only message + type.

Corrections to #112's attachment model

• EmailEventAttachment.Id: Guid → string. The server types it as a plain string and inbound attachment ids are not UUIDs; Guid would throw at deserialization. (The new inbound test uses "att_123" to cover this.)
• filename, content_disposition, content_id made nullable to match the server (string | null).

Tests

3 new raw-JSON deserialization tests in Resend.Webhooks.Tests (real server-style payloads for opened, received, suppressed). Full suite on .NET 8: all pass (Webhooks 6/6).

Note

suppressed.reason/type are modeled as string (documented enum values in remarks) rather than enums, consistent with the existing bounce.type/subType treatment in this file.

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Summary by cubic

Completes EmailEventData parity with the Resend webhook payload and fixes attachment modeling to match the API. Ensures open events, headers, inbound recipients, and suppression details deserialize correctly.

• New Features

  • open (EmailOpenData: ipAddress, timestamp, userAgent) for email.opened.
  • headers (List<EmailEventHeader>) on all events.
  • received_for (EmailAddressList) for inbound email.received.
  • suppressed.reason and suppressed.diagnosticCode.

• Bug Fixes

  • EmailEventAttachment.Id: Guid → string to prevent deserialization errors.
  • filename, content_disposition, content_id are now nullable to match the server.
  • Added raw JSON deserialization tests for opened, received, and suppressed events.

^{Written for commit 55ebbba. Summary will update on new commits.}

[cubic-dev-ai]

No issues found across 4 files

Confidence score: 5/5

• Automated review surfaced no issues in the provided summaries.
• No files require special attention.

<sub>Auto-approved: Adds missing webhook email fields (open, headers, received_for, suppressed) and fixes attachment ID type to prevent deserialization errors. Low-risk changes with accompanying tests.

Re-trigger cubic</sub>