Create AcquiaDamWebhookClient and Submodule Scaffold.

Problem/Motivation

As a site admin, I want the acquia_dam_webhooks submodule scaffolded with its .info.yml + .services.yml and a AcquiaDamWebhookClient service owning all webhook API methods, so that webhook API concerns are fully self-contained in the submodule (parent AcquiaDamClient has zero webhook code) and the submodule can be enabled as a standalone opt-in feature.

Context

The 6 webhook CRUD/ping methods live in AcquiaDamWebhookClient inside the submodule.

The parent AcquiaDamClient should remain free of webhook-specific code.

AcquiaDamWebhookClient delegates HTTP transport to AcquiaDamClientFactory::getSiteClient() and exception translation to DamExceptionHandler.

Acceptance Criteria

• AcquiaDamWebhookClient exists in Drupal\acquia_dam_webhooks\Client\AcquiaDamWebhookClient.
• It owns all 6 webhook API methods:
  • createWebhook(string $event_type, string $delivery_url, string $secret_key): array — POST /v2/webhooks/configurations
  • listWebhooks(): array — GET /v2/webhooks/configurations
  • getWebhook(string $id): array — GET /v2/webhooks/configurations/{id}
  • updateWebhook(string $id, array $data): array — PUT /v2/webhooks/configurations/{id}
  • deleteWebhook(string $id): bool — DELETE /v2/webhooks/configurations/{id} returns TRUE on 204
  • pingWebhook(string $id): bool — GET /v2/webhooks/configurations/{id}/ping returns TRUE on 200
• It injects AcquiaDamClientFactory for HTTP transport via getSiteClient().
• It injects DamExceptionHandler for exception translation.
• All methods follow the existing pattern: try/catch + DamExceptionHandler::handle() → DamClientException / DamServerException / DamConnectException.
• Registered as acquia_dam_webhooks.client in acquia_dam_webhooks.services.yml.
• acquia_dam_webhooks.info.yml declares dependencies: [acquia_dam:acquia_dam] and package: 'Acquia DAM'.
• acquia_dam_webhooks.services.yml registers acquia_dam_webhooks.client and the acquia_dam_webhooks.webhook_manager service (constructor injects AcquiaDamWebhookClient — all DAM webhook API calls route through acquia_dam_webhooks.client).