Update user agent parsing and added new UA for updating sigv4 override

Author: kai-ion

src/aws-cpp-sdk-core/source/auth/signer/AWSAuthV4Signer.cpp

@@ -632,45 +632,62 @@ void AWSAuthV4Signer::UpdateUserAgentWithCredentialFeatures(Aws::Http::HttpReque
     }
 
     Aws::StringStream credentialFeatures;
-    bool first = true;
     for (const auto& feature : features) {
         Aws::String featureStr;
         switch (feature) {
             case Aws::Client::UserAgentFeature::CREDENTIALS_ENV_VARS:
                 featureStr = "g";
                 break;
             case Aws::Client::UserAgentFeature::CREDENTIALS_SIGV4_SIGNER:
-                featureStr = "MD";
+                if (request.HasHeader(USER_AGENT)) {
+                    auto userAgentParts = Aws::Utils::StringUtils::Split(request.GetHeaderValue(USER_AGENT), ' ');
+                    
+                    // Find position to insert metadata (before metrics section)
+                    auto metricsIt = std::find_if(userAgentParts.begin(), userAgentParts.end(),
+                        [](const Aws::String& part) { return part.find("m/") == 0; });
+                        
+                    // Insert metadata at appropriate position
+                    userAgentParts.insert(metricsIt, "md/override_get_credentials");
+                    
+                    // Reassemble with spaces
+                    Aws::String newUserAgent = userAgentParts.front();
+                    for (auto it = std::next(userAgentParts.begin()); it != userAgentParts.end(); ++it) {
+                        newUserAgent += " " + *it;
+                    }
+                    request.SetHeaderValue(USER_AGENT, newUserAgent);
+                }
                 break;
             default:
                 break;
         }
+        
         if (!featureStr.empty()) {
-            if (!first) {
+            if (!credentialFeatures.str().empty()) {
                 credentialFeatures << ",";
             }
             credentialFeatures << featureStr;
-            first = false;
         }
     }
 
     if (!credentialFeatures.str().empty()) {
-        Aws::String existingUA = request.GetHeaderValue(USER_AGENT);
-        size_t mPos = existingUA.find(" m/");
+        Aws::String userAgent = request.GetHeaderValue(USER_AGENT);
+        auto userAgentParsed = Aws::Utils::StringUtils::Split(userAgent, ' ');
+        auto metricsSegment = std::find_if(userAgentParsed.begin(), userAgentParsed.end(), 
+            [](const Aws::String& value) { return value.find("m/") != Aws::String::npos; });
 
-        if (mPos != Aws::String::npos) {
-            // "m/" section already exists, find where to insert our metrics
-            size_t metricsStart = mPos + 3; // Position after "m/"
-            size_t nextSectionPos = existingUA.find(" ", metricsStart);
-            
-            // Insert our metrics with comma separator at the end of existing metrics
-            Aws::String newUA = existingUA;
-            newUA.insert(nextSectionPos != Aws::String::npos ? nextSectionPos : existingUA.length(), 
-                        "," + credentialFeatures.str());
-            request.SetUserAgent(newUA);
+        if (metricsSegment != userAgentParsed.end()) {
+            // Add new metrics to existing metrics section
+            *metricsSegment = Aws::String{*metricsSegment + "," + credentialFeatures.str()};
         } else {
-            // No existing "m/" section, add it
-            request.SetUserAgent(existingUA + " m/" + credentialFeatures.str());
+            // No metrics section exists, add new one
+            userAgentParsed.push_back("m/" + credentialFeatures.str());
+        }
+        
+        // Reassemble all parts with spaces
+        Aws::String newUserAgent = userAgentParsed.front();
+        for (auto it = std::next(userAgentParsed.begin()); it != userAgentParsed.end(); ++it) {
+            newUserAgent += " " + *it;
         }
+        request.SetUserAgent(newUserAgent);
     }
 }

tests/aws-cpp-sdk-core-tests/aws/auth/CredentialTrackingTest.cpp

@@ -177,9 +177,9 @@ TEST_F(CredentialTrackingTest, TestLegacySigV4SignerTracking)
     }
     EXPECT_EQ(1, mSectionCount);
 
-    // Check for legacy SigV4 signer business metric (MD) in user agent
+    // Check for legacy SigV4 signer business metric (md/override_get_credentials) in user agent
     auto businessMetrics = std::find_if(userAgentParsed.begin(), userAgentParsed.end(),
-        [](const Aws::String& value) { return value.find("m/") != Aws::String::npos && value.find("MD") != Aws::String::npos; });
+        [](const Aws::String& value) { return value.find("md/override_get_credentials") != Aws::String::npos; });
 
     EXPECT_TRUE(businessMetrics != userAgentParsed.end());
 }