Support CUR 2.0/BCM Data Export Configuration at Individual Linked Account Level in Vendor Credentials API

Currently the Cloudability vendor credentials API link account resource only accepts three fields vendor Account ID , type and region. The CUR configuration at the linked account level is not supported . Individual linked accounts inherit CUR configuration entirely from the master payer enrolled via master connect 

This creates two specific gaps 
Gap 1 : Test environment  where in customers with a separate Cloudability test instance cannot enroll linked accounts because there is no master payer in test instance . Without a master payer Cloudability requires explicit CUR fields at the enrollment time but the link account API doesnot support providing them 

Gap 2 : CUR 2.0 migration cannot be validated at individual account level .CUR 2.0 migration via master_connect is supported at the master payer level only. There is no way to configure or validate CUR 2.0 at the individual linked account level where customers cannot have a separate payer account for test . This means customers cannot validate or test CUR 2.0 data for individual accounts before commiting to a full master payer level migration.

We request that the link_account API resource be updated to accept CUR 2.0 / BCM Data Export configuration fields specifically bucketName, costAndUsageReport name, costAndUsageReport prefix, and region. This would allow individual linked accounts to be enrolled in a Cloudability test instance without requiring a master payer, enable per account CUR 2.0 configuration and validation independently of the master payer, and support programmatic enrollment at scale via Terraform for CUR 2.0.