lint: address latest lint's from msrv update

First: update default_features to default-features in cargo.toml
Second: replace get(0) with first()

Cargo.toml

@@ -37,13 +37,13 @@ debug = true
 anyhow = "1.0"
 base64 = "0.21"
 cfg-if = "1.0"
-clap = { version = "4", "default_features" = false, "features" = ["std", "cargo", "derive", "error-context", "help", "suggestions", "usage", "wrap_help"] }
+clap = { version = "4", "default-features" = false, "features" = ["std", "cargo", "derive", "error-context", "help", "suggestions", "usage", "wrap_help"] }
 ipnetwork = ">= 0.17, < 0.21"
 libflate = "1.3"
 libsystemd = ">= 0.2.1, < 0.8.0"
 mailparse = ">= 0.13, < 0.16"
 maplit = "1.0"
-nix = { version = ">= 0.19, < 0.29", "default_features" = false, "features" = [ "mount", "user"] }
+nix = { version = ">= 0.19, < 0.29", "default-features" = false, "features" = [ "mount", "user"] }
 openssh-keys = ">= 0.5, < 0.7"
 openssl = ">= 0.10.46, < 0.11"
 pnet_base = ">= 0.26, < 0.35"

src/providers/microsoft/goalstate.rs

@@ -14,7 +14,7 @@ pub(crate) struct GoalState {
 impl GoalState {
     /// Return the certificates endpoint (if any).
     pub(crate) fn certs_endpoint(&self) -> Option<String> {
-        let role = match self.container.role_instance_list.role_instances.get(0) {
+        let role = match self.container.role_instance_list.role_instances.first() {
             Some(r) => r,
             None => return None,
         };
@@ -33,7 +33,7 @@ impl GoalState {
             .container
             .role_instance_list
             .role_instances
-            .get(0)
+            .first()
             .ok_or_else(|| anyhow!("empty RoleInstanceList"))?
             .instance_id)
     }