Vault proxy

Footprint is the custodian of your users' most sensitive information, and your app sometimes needs to send that information to third-party services. The Vault Proxy sends your users' data directly to third parties you configure, so your app never touches sensitive data in plaintext. It also vaults new information from those third parties into your users' vaults, again without your code handling sensitive data.

For upstreams you call often, you can preconfigure the egress request headers and body.

The Vault Proxy article covers it in depth.