feat(webhooks): add event replay endpoint

[gabrielmfern]

Adds POST /webhooks/{webhook_id}/events/{event_id}/replay (webhooks/replay-event), which queues one more delivery of a webhook event to its webhook. Placed next to get_event / get_event_async, same argument style.

def replay_event(cls, webhook_id: str, event_id: str) -> ReplayEventResponse
async def replay_event_async(cls, webhook_id: str, event_id: str) -> ReplayEventResponse

ReplayEventResponse is { object: "webhook_event", id: str }.

import resend

resend.api_key = "re_xxxxxxxxx"

replayed = resend.Webhooks.replay_event(
    "4dd369bc-aa82-4ff3-97de-514ae3000ee0", "msg_1srOrx2ZWZBpBUvZwXKQmoEYga2"
)
print(replayed["id"])

Also adds a replay call to examples/webhooks.py.

Spec PR: resend/resend-openapi#112
API PR: https://github.com/resend/resend-monorepo/pull/9535
Docs page: https://resend.com/docs/api-reference/webhooks/replay-event

Tests

The ResendBaseTest fixture mocks Request.make_request(url), which hides the verb, and the verb is the only thing separating replay_event from get_event. The tests therefore swap resend.default_http_client / resend.default_async_http_client for a mock client and assert method == "post" plus the exact URL, the same shape as TestSuppressionsRequestBody. The setUp/tearDown is copied rather than lifted into conftest.py on purpose: this is the second copy per mode, not the third.

Checks

• tox -e lint (flake8): passed
• tox -e mypy: passed, no issues in 181 files
• tox -e py (pytest): 626 passed

Not verified live

No call was made against the API (write endpoint, no key configured for this task). The tests pin the verb and path; the only remaining assumption is the response body shape, which is pinned by the spec (ReplayWebhookEventResponse).

No version bump; that happens in a separate chore PR.

Part of DEV-2005.

Linear: https://linear.app/resend/issue/DEV-2012

[cubic-dev-ai]

All reported issues were addressed

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[cubic-dev-ai]

All reported issues were addressed across 1 file (changes from recent commits).

<sub>Requires human review: Auto-approval blocked by 1 unresolved issue from previous reviews.

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[cubic-dev-ai]

0 issues found across 2 files (changes from recent commits).

Confidence score: 5/5

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

<sub>Requires human review: Adds a public POST endpoint that triggers an additional webhook delivery. Human review is needed for the product and operational implications of replay semantics and its external API contract.

Re-trigger cubic</sub>

[cubic-dev-ai]

All reported issues were addressed across 2 files (changes from recent commits).

<sub>Tip: Review your code locally with the cubic CLI to iterate faster.

Re-trigger cubic</sub>

[cubic-dev-ai]

0 issues found across 2 files (changes from recent commits).

Confidence score: 5/5

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

<sub>Requires human review: Adds a new public POST endpoint that queues an additional webhook delivery. Human review is needed for the product and operational semantics of replay and the new external API contract.

Re-trigger cubic</sub>