Add webhook custom delivery headers to docs and SDKs

[mikesteroonie]

Summary

• add the optional headers map to organization-, pod-, and inbox-scoped webhook creation
• add typed GET .../headers and PATCH .../headers endpoints across all three SDK namespaces
• document write-only header values, safe name inspection, atomic rotation, and removal

Why

The backend support shipped in agentmail-api PRs #710 and #728, but the Fern contract did not yet expose it to generated SDKs or API reference users. This change lets developers authenticate and route webhook deliveries without recreating endpoints, while keeping secret values out of read responses.

SDK impact

Generated clients gain:

• Python: get_headers() and update_headers()
• TypeScript: getHeaders() and updateHeaders()
• headers on webhook creation at organization, pod, and inbox scope

Validation

• fern check: 0 errors; only pre-existing route-conflict warnings plus the existing FDR redirect-check warning
• git diff --cached --check
• local SDK generation reached both configured generators but could not execute because Docker is unavailable in the environment; repository release workflows will generate the SDKs from the validated Fern contract

[github-actions]

🌿 Preview your docs: https://agentmail-preview-e56d039a-73f6-4013-8015-f7509612eba0.docs.buildwithfern.com

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[github-actions]

✨ API Changes

# API Changelog n/a vs. n/a


## API Changes

### POST /v0/inboxes/{inbox_id}/webhooks
-  added the new optional request property `headers`


### GET /v0/inboxes/{inbox_id}/webhooks/{webhook_id}/headers
-  endpoint added


### PATCH /v0/inboxes/{inbox_id}/webhooks/{webhook_id}/headers
-  endpoint added


### POST /v0/pods/{pod_id}/webhooks
-  added the new optional request property `allOf[subschema #1: webhooksCreateInboxWebhookRequest]/headers`


### GET /v0/pods/{pod_id}/webhooks/{webhook_id}/headers
-  endpoint added


### PATCH /v0/pods/{pod_id}/webhooks/{webhook_id}/headers
-  endpoint added


### POST /v0/webhooks
-  added the new optional request property `allOf[subschema #1: webhooksCreatePodWebhookRequest]/allOf[subschema #1: webhooksCreateInboxWebhookRequest]/headers`


### GET /v0/webhooks/{webhook_id}/headers
-  endpoint added


### PATCH /v0/webhooks/{webhook_id}/headers
-  endpoint added

💡 Download api-changelog-diff artifact or tag @fern Writer in #github-prs for changelog.

[github-actions]

✨ API Changes

# API Changelog n/a vs. n/a


## API Changes

### POST /v0/inboxes/{inbox_id}/webhooks
-  added the new optional request property `headers`


### GET /v0/inboxes/{inbox_id}/webhooks/{webhook_id}/headers
-  endpoint added


### PATCH /v0/inboxes/{inbox_id}/webhooks/{webhook_id}/headers
-  endpoint added


### POST /v0/pods/{pod_id}/webhooks
-  added the new optional request property `allOf[subschema #1: webhooksCreateInboxWebhookRequest]/headers`


### GET /v0/pods/{pod_id}/webhooks/{webhook_id}/headers
-  endpoint added


### PATCH /v0/pods/{pod_id}/webhooks/{webhook_id}/headers
-  endpoint added


### POST /v0/webhooks
-  added the new optional request property `allOf[subschema #1: webhooksCreatePodWebhookRequest]/allOf[subschema #1: webhooksCreateInboxWebhookRequest]/headers`


### GET /v0/webhooks/{webhook_id}/headers
-  endpoint added


### PATCH /v0/webhooks/{webhook_id}/headers
-  endpoint added

💡 Download api-changelog-diff artifact or tag @fern Writer in #github-prs for changelog.

[github-actions]

🌿 Preview your docs: https://agentmail-preview-3af51d01-f406-426d-9b44-62173e96c6f4.docs.buildwithfern.com