* VAULT-12940 test for templating user agent
* VAULT-12940 User agent work so far
* VAULT-12940 Vault Agent uses Vault Agent specific User-Agent header when issuing requests
* VAULT-12940 Clean-up and godocs
* VAULT-12940 changelog
* VAULT-12940 Fix test checking headers
* VAULT-12940 Fix test checking headers
* VAULT-12940 Fix test checking headers
* VAULT-12940 Fix test checking headers
* VAULT-12940 copy/paste typos
* VAULT-12940 improve comments, use make(http.Header)
* VAULT-12940 small typos and clean-up