Gate connected-account webhook subscriptions behind config (#22761)

Now gated behind IS_CONNECTED_ACCOUNT_WEBHOOK_SUBSCRIPTION_ENABLED
(default false).

Merge + deploy twentyhq/twenty-infra#780 first.

<!-- This is an auto-generated description by cubic. -->
<a
href="https://cubic.dev/pr/twentyhq/twenty/pull/22761?utm_source=github"
target="_blank" rel="noopener noreferrer"
data-no-image-dialog="true"><picture><source
media="(prefers-color-scheme: dark)"
srcset="https://www.cubic.dev/buttons/review-in-cubic-dark.svg"><source
media="(prefers-color-scheme: light)"
srcset="https://www.cubic.dev/buttons/review-in-cubic-light.svg"><img
alt="Review in cubic"
src="https://www.cubic.dev/buttons/review-in-cubic-dark.svg"></picture></a>
<!-- End of auto-generated description by cubic. -->

Co-authored-by: Charles Bochet <charlesBochet@users.noreply.github.com>

packages/twenty-server/src/engine/core-modules/twenty-config/config-variables.ts

@@ -209,6 +209,16 @@ export class ConfigVariables {
   @IsOptional()
   MESSAGING_GMAIL_PUBSUB_VERIFICATION_EMAIL: string;
 
+  @ConfigVariablesMetadata({
+    group: ConfigVariablesGroup.ADVANCED_SETTINGS,
+    description:
+      'Enable webhook-based sync for connected accounts (provider push ' +
+      'notifications on top of polling). Requires publicly reachable ' +
+      'webhook endpoints.',
+    type: ConfigVariableType.BOOLEAN,
+  })
+  IS_CONNECTED_ACCOUNT_WEBHOOK_SUBSCRIPTION_ENABLED = false;
+
   @ConfigVariablesMetadata({
     group: ConfigVariablesGroup.ADVANCED_SETTINGS,
     description: 'Enable or disable the IMAP messaging integration',