secretArn 
  The Amazon Resource Name (ARN) of an Secrets Managersecret that contains the key/value pairs required to connect to your Salesforce instance. The secret must contain a JSON structure with the following keys:
- authenticationUrl - The OAUTH endpoint that Amazon Kendra connects to get an OAUTH token. 
- consumerKey - The application public key generated when you created your Salesforce application. 
- consumerSecret - The application private key generated when you created your Salesforce application. 
- password - The password associated with the user logging in to the Salesforce instance. 
- securityToken - The token associated with the user logging in to the Salesforce instance. 
- username - The user name of the user logging in to the Salesforce instance.