Credentials: Fetching AWS creds for ``/document`` endpoints

Describe the bug
Currently, document upload and fetching related endpoints are directly accessing AWS credentials without fetching them through the organization and project-specific logic. This bypasses the necessary logic to ensure that AWS credentials are scoped by org_id and project_id.

Expected Behavior:

1. The document endpoints should fetch AWS credentials using get_provider_credential scoped by org_id and project_id.

2. If the credentials are missing or invalid, the endpoint should return a clear failure response (e.g., 400 Bad Request with a message like "AWS credentials are missing or invalid").

3. The project_id should be correctly passed in the request and used when fetching AWS credentials.

ドキュメントのアップロードおよび取得エンドポイントから始めて、現在どのように AWS 認証情報へアクセスしているかを追跡します。その経路を get_provider_credential と比較し、org_id と project_id が渡されていること、また認証情報がない場合や無効な場合に指定された失敗レスポンスが返されることを確認します。