Get overview metrics for Google Ads account for a specified date range.
Args: customer_id: The Google Ads customer ID login_customer_id: Optional manager account ID start_date (str): Start date for the data range (YYYY-MM-DD). Defaults to 30 days ago. end_date (str): End date for the data range (YYYY-MM-DD). Defaults to today. oauth2_token: OAuth2 token for authentication
Returns: OverviewData: Account performance summary
The access token received from the authorization server in the OAuth 2.0 flow.