Vault Agent - Allow auto_auth without specifying a sink

For a personal project I really need to write up, I’m using the HashiCorp Vault Agent to auto authenticate to AWS and write out some dynamic creds; for my use case I don’t have any need for the resultant Vault token outside of the Agent.

I quickly ran into an outstanding issue trying to do that, in that you had to do something with the token; either write it out, or have the Agent act as a local cache for Vault queries. In my case, I didn’t need to do either, and as evidenced here other folks were running into that as well.

In the course of digging through the code to figure out what was going on, I was halfway through figuring out enough to fix it, so I plugged away at it and contributed this [pull request] (https://github.com/hashicorp/vault/pull/8812). After some back and forth, in which I learned some new stuff in the Agent test suite, that request was merged in.

Digging through what it took to get the test suite updated and passing was very useful — I just don’t have much experience with how Golang does testing so it was good to exercise that in my brain. And once again I find it an absolute pleasure to work in the Vault code, it’s an insanely well-thought out and written piece of software.

Standard Disclaimer: HashiCorp applies.