Sync integration installations

- **GitHub**: Fetches GitHub App installations and syncs their repositories. - **GitLab**: Refreshes accessible projects for linked accounts and syncs them as repositories.

curl -X POST "https://example.com/v1/integrations/string/installations" \  -H "Content-Type: application/json" \  -d '{}'

{  "installations": [    {      "account_name": "string",      "account_type": "string",      "created_at": 0,      "external_id": "string",      "id": "string",      "integration_id": "string"    }  ]}