fix(tests): resolve all clippy warnings for CI compliance

- Remove needless borrows on format!() in set_body_string() calls (needless_borrows_for_generic_args)
- Replace assert!(false, ...) with collected assertion (assertions_on_constants + never_loop)
- Use direct Method::POST comparison instead of to_string() (cmp_owned)
- Simplify negated equality to != operator (nonminimal_bool)

CI pipeline now passes with -D warnings enabled

tests/e2e/test_enrollment_e2e.rs

@@ -120,7 +120,7 @@ async fn test_full_enrollment_flow_happy_path() {
         .and(path("/api/v1/enroll"))
         .respond_with(
             ResponseTemplate::new(202)
-                .set_body_string(&format!(r#"{{"polling_token": "{}"}}"#, TEST_TOKEN)),
+                .set_body_string(format!(r#"{{"polling_token": "{}"}}"#, TEST_TOKEN)),
         )
         .named("enroll_registration")
         .mount(&server)
@@ -135,7 +135,7 @@ async fn test_full_enrollment_flow_happy_path() {
                 ResponseTemplate::new(200).set_body_string(r#"{"status": "pending"}"#)
             } else {
                 // Second poll returns approved with full PKI bundle
-                ResponseTemplate::new(200).set_body_string(&format!(
+                ResponseTemplate::new(200).set_body_string(format!(
                     r#"{{
                         "status": "approved",
                         "ca_crt": {},
@@ -414,7 +414,7 @@ async fn test_certificate_permission_verification() {
 
     Mock::given(method("GET"))
         .and(path_regex(r"/api/v1/enroll/status/.+"))
-        .respond_with(ResponseTemplate::new(200).set_body_string(&format!(
+        .respond_with(ResponseTemplate::new(200).set_body_string(format!(
             r#"{{
                     "status": "approved",
                     "ca_crt": {},
@@ -529,7 +529,7 @@ async fn test_whitelist_append_verification() {
 
     Mock::given(method("GET"))
         .and(path_regex(r"/api/v1/enroll/status/.+"))
-        .respond_with(ResponseTemplate::new(200).set_body_string(&format!(
+        .respond_with(ResponseTemplate::new(200).set_body_string(format!(
             r#"{{
                     "status": "approved",
                     "ca_crt": {},
@@ -663,14 +663,15 @@ async fn test_signal_handling_during_polling() {
     );
 
     // Verify: cleanup of any partial state (no leftover files)
-    for entry in std::fs::read_dir(cert_dir.path()).unwrap() {
-        let entry = entry.unwrap();
-        assert!(
-            false,
-            "No partial files should remain after graceful shutdown: {}",
-            entry.file_name().to_string_lossy()
-        );
-    }
+    let remaining: Vec<_> = std::fs::read_dir(cert_dir.path())
+        .unwrap()
+        .map(|e| e.unwrap().file_name().to_string_lossy().to_string())
+        .collect();
+    assert!(
+        remaining.is_empty(),
+        "No partial files should remain after graceful shutdown: {:?}",
+        remaining
+    );
 }
 
 // =============================================================================
@@ -703,7 +704,7 @@ async fn test_whitelist_yaml_format_preservation() {
 
     Mock::given(method("GET"))
         .and(path_regex(r"/api/v1/enroll/status/.+"))
-        .respond_with(ResponseTemplate::new(200).set_body_string(&format!(
+        .respond_with(ResponseTemplate::new(200).set_body_string(format!(
             r#"{{
                     "status": "approved",
                     "ca_crt": {},

tests/integration/enrollment_test.rs

@@ -11,6 +11,7 @@
 
 use linux_patch_api::enroll::client::EnrollmentClient;
 use serial_test::serial;
+use wiremock::http::Method;
 use wiremock::{
     matchers::{method, path, path_regex},
     Mock, MockServer, ResponseTemplate,
@@ -417,7 +418,7 @@ async fn test_registration_payload_structure() {
     let requests = server.received_requests().await.unwrap();
     let post_request = requests
         .iter()
-        .find(|r| r.method.to_string() == "POST")
+        .find(|r| r.method == Method::POST)
         .expect("Should have received a POST request");
 
     let body_str = std::str::from_utf8(&post_request.body).expect("Body should be valid UTF-8");

tests/unit/enroll_identity.rs

@@ -245,7 +245,7 @@ fn test_ip_addresses_are_unicast() {
 
         // Not unspecified (0.0.0.0)
         assert!(
-            !(parts == vec![0, 0, 0, 0]),
+            parts != vec![0, 0, 0, 0],
             "Address '{}' is unspecified",
             addr
         );
@@ -492,7 +492,7 @@ fn test_cross_distro_os_release_parsing() {
         parsed.contains_key("NAME"),
         "os-release must contain NAME field"
     );
-    assert!(parsed["NAME"].ne(&""), "NAME should not be empty");
+    assert!(!parsed["NAME"].is_empty(), "NAME should not be empty");
 }
 
 #[test]