feat(1.0.0): Handle custom way for Kubernetes

Kubernetes now uses K8S_SERVICE_ACCOUNT to set the path instead of VAULT_K8S_AUTH_PATH.
VAULT_K8S_AUTH_PATH is now optional and allows to specify the name of in the auth URL.

Cargo.toml

@@ -1,7 +1,7 @@
 [package]
 name = "vault-credentials"
 description = "Rust Library that fetch secrets from Vault and load them as environment variables."
-version = "0.4.1"
+version = "1.0.0"
 authors = ["Lucas Perreau <[email protected]>"]
 edition = "2018"
 license = "MIT OR Apache-2.0"
@@ -27,4 +27,4 @@ tokio = { version = "1.5.0", features = ["full"] }
 serde_json = "1.0.63"
 
 [dev-dependencies]
-dotenv = "0.15.0"
+dotenv = "0.15.0"