Plaid Retrieve an Asset Report Audit Copy

`/asset_report/audit_copy/get` allows auditors to get a copy of an Asset Report that was previously shared via the `/asset_report/audit_copy/create` endpoint. The caller of `/asset_report/audit_copy/create` must provide the `audit_copy_token` to the auditor. This token can then be used to call `/asset_report/audit_copy/create`.