Make SignedHeaderRequirements a trait

This allows easier use for the typical case, where the SignedHeaders
is either empty or is initialized from static string slices. This
has the side benefit of removing allocations in the common case.

Author: dacut

src/aws4.rs

@@ -1,7 +1,7 @@
 use {
     crate::{
         service_for_signing_key_fn, sigv4_validate_request, CanonicalRequest, GetSigningKeyRequest,
-        GetSigningKeyResponse, KSecretKey, SignatureOptions, SignedHeaderRequirements,
+        GetSigningKeyResponse, KSecretKey, SignatureOptions, NO_ADDITIONAL_SIGNED_HEADERS,
     },
     bytes::{Bytes, BytesMut},
     chrono::{DateTime, NaiveDate, NaiveDateTime, NaiveTime, Utc},
@@ -226,8 +226,8 @@ async fn run(basename: &str) {
     expected_canonical_request.retain(|c| *c != b'\r'); // Remove carriage returns (not newlines)
 
     // Check the canonical request.
-    let req = SignedHeaderRequirements::default();
-    let auth_params = canonical.get_auth_parameters(&req).expect("Failed to get auth parameters");
+    let auth_params =
+        canonical.get_auth_parameters(&NO_ADDITIONAL_SIGNED_HEADERS).expect("Failed to get auth parameters");
     let canonical_request = canonical.canonical_request(&auth_params.signed_headers);
     assert_eq!(
         String::from_utf8_lossy(canonical_request.as_slice()),
@@ -273,14 +273,13 @@ async fn run(basename: &str) {
     // Create a GetSigningKeyRequest from our existing request.
     debug!("body: {:?}", body);
     let request = Request::from_parts(parts, body);
-    let required_headers = SignedHeaderRequirements::default();
     sigv4_validate_request(
         request,
         TEST_REGION,
         TEST_SERVICE,
         &mut signing_key_svc,
         test_time,
-        &required_headers,
+        &NO_ADDITIONAL_SIGNED_HEADERS,
         SignatureOptions::url_encode_form(),
     )
     .await