Creates an object which contains the information required to access data in the Secure Credentials Store.
a!scsField( externalSystemKey, fieldKey, usePerUser)
externalSystemKey (Text): The key of the corresponding external system in the Third Party Credentials admin console page.
fieldKey (Text): The key for the field which stores the requested data.
usePerUser (Boolean): If true, the current user's credentials for the third party system will be used. If false, the system-wide credentials for the third party system will be used. Default: false.
