Move ApplyUserAgentStage to later position in request pipeline

Author: S-Saranya1

.changes/next-release/feature-AWSSDKforJavav2-5eb5d9f.json

@@ -0,0 +1,6 @@
+{
+    "type": "feature",
+    "category": "AWS SDK for Java v2",
+    "contributor": "",
+    "description": "Move `ApplyUserAgentStage` to later position in request pipeline to ensure all business metrics are properly recorded before finalizing user agent."
+}

core/sdk-core/src/main/java/software/amazon/awssdk/core/internal/http/AmazonAsyncHttpClient.java

@@ -193,12 +193,12 @@ public <OutputT> CompletableFuture<OutputT> execute(
                         .first(RequestPipelineBuilder
                                 .first(MakeRequestMutableStage::new)
                                 .then(ApplyTransactionIdStage::new)
-                                .then(ApplyUserAgentStage::new)
                                 .then(MergeCustomHeadersStage::new)
                                 .then(MergeCustomQueryParamsStage::new)
                                 .then(QueryParametersToBodyStage::new)
                                 .then(() -> new CompressRequestStage(httpClientDependencies))
                                 .then(() -> new HttpChecksumStage(ClientType.ASYNC))
+                                .then(ApplyUserAgentStage::new)
                                 .then(MakeRequestImmutableStage::new)
                                 .then(RequestPipelineBuilder
                                         .first(AsyncSigningStage::new)

core/sdk-core/src/main/java/software/amazon/awssdk/core/internal/http/AmazonSyncHttpClient.java

@@ -181,12 +181,12 @@ public <OutputT> OutputT execute(HttpResponseHandler<Response<OutputT>> response
                     .first(RequestPipelineBuilder
                                .first(MakeRequestMutableStage::new)
                                .then(ApplyTransactionIdStage::new)
-                               .then(ApplyUserAgentStage::new)
                                .then(MergeCustomHeadersStage::new)
                                .then(MergeCustomQueryParamsStage::new)
                                .then(QueryParametersToBodyStage::new)
                                .then(() -> new CompressRequestStage(httpClientDependencies))
                                .then(() -> new HttpChecksumStage(ClientType.SYNC))
+                               .then(ApplyUserAgentStage::new)
                                .then(MakeRequestImmutableStage::new)
                                // End of mutating request
                                .then(RequestPipelineBuilder