Add webhook migration support

[premtsd-code]

Summary

Stacks on #184. Adds webhook as a migrable resource.

• Source: Appwrite SDK Webhooks::list() (separate service from Project) with cursor pagination. Reports via reportIntegrations.
• Destination: direct dbForPlatform->createDocument('webhooks', ...) matching the upstream Webhooks::Create payload exactly.

Notes

• Resource::TYPE_WEBHOOK = 'webhook', placed in GROUP_INTEGRATIONS_RESOURCES.
• Carries through name, url, events, security (TLS), httpUser/httpPass (basic auth), and enabled.
• Signing secret regenerates: the SDK strips signatureKey on list responses (Webhooks/XList.php explicitly removeAttribute('signatureKey')). Destination generates a fresh bin2hex(random_bytes(64)) to match upstream's createWebhook default. Webhook receivers verifying signatures must be updated with the destination's new key.

[greptile-apps]

Greptile Summary

This PR adds webhook as a migratable resource, covering export from the Appwrite SDK's Webhooks::list() and direct import into dbForPlatform via createWebhook(). The group routing, dispatch, and field mapping are all correct in the final state.

• Source (Sources/Appwrite.php): exportWebhooks() uses cursor pagination via the dedicated Webhooks service; tls→security and authUsername/authPassword→httpUser/httpPass mappings are intentional.
• Destination (Destinations/Appwrite.php): createWebhook() writes to dbForPlatform, regenerates signatureKey with bin2hex(random_bytes(64)) matching upstream behavior, and purges the project cache on success.
• Resource class (Resources/Settings/Webhook.php): getGroup() correctly returns Transfer::GROUP_INTEGRATIONS, so the dispatch router in importIntegrationsResource() reaches createWebhook() as expected.

Confidence Score: 5/5

Safe to merge; the webhook resource is correctly wired end-to-end from export through import.

The group routing, dispatch switch, and DB write all connect correctly. The one comment-placement nit in Resource.php has no runtime effect. Previously flagged concerns have been addressed or are pre-existing patterns shared with other resource types.

No files require special attention.

Important Files Changed

Filename	Overview
src/Migration/Destinations/Appwrite.php	Adds createWebhook() to the platform DB, dispatched via importIntegrationsResource; dedup uses name-only match (pre-flagged); fresh signatureKey generation is correct.
src/Migration/Sources/Appwrite.php	Adds exportWebhooks() using the Webhooks SDK service with cursor pagination; field mapping (tls→security, authUsername→httpUser) is correct.
src/Migration/Resources/Settings/Webhook.php	New Webhook resource class with correct getGroup() returning GROUP_INTEGRATIONS; all getters implemented cleanly.
src/Migration/Resource.php	TYPE_WEBHOOK constant added but placed under the // Settings comment section instead of // Integrations, creating a misleading classification.
src/Migration/Transfer.php	TYPE_WEBHOOK correctly added to GROUP_INTEGRATIONS_RESOURCES and ALL_PUBLIC_RESOURCES under the // Integrations section.
tests/Migration/Unit/Adapters/MockDestination.php	TYPE_WEBHOOK and TYPE_PROJECT_VARIABLE added to supported resources list.
tests/Migration/Unit/Adapters/MockSource.php	TYPE_WEBHOOK and TYPE_PROJECT_VARIABLE added to supported resources list.

_{Reviews (8): Last reviewed commit: "Register TYPE_PROJECT_VARIABLE and TYPE_..." | Re-trigger Greptile}

[abnegate]

Let's group this with integrations