s3/iam: reuse one request id per request (#8538)

* request_id: add shared request middleware

* s3err: preserve request ids in responses and logs

* iam: reuse request ids in XML responses

* sts: reuse request ids in XML responses

* request_id: drop legacy header fallback

* request_id: use AWS-style request id format

* iam: fix AWS-compatible XML format for ErrorResponse and field ordering

- ErrorResponse uses bare <RequestId> at root level instead of
  <ResponseMetadata> wrapper, matching the AWS IAM error response spec
- Move CommonResponse to last field in success response structs so
  <ResponseMetadata> serializes after result elements
- Add randomness to request ID generation to avoid collisions
- Add tests for XML ordering and ErrorResponse format

* iam: remove duplicate error_response_test.go

Test is already covered by responses_test.go.

* address PR review comments

- Guard against typed nil pointers in SetResponseRequestID before
  interface assertion (CodeRabbit)
- Use regexp instead of strings.Index in test helpers for extracting
  request IDs (Gemini)

* request_id: prevent spoofing, fix nil-error branch, thread reqID to error writers

- Ensure() now always generates a server-side ID, ignoring client-sent
  x-amz-request-id headers to prevent request ID spoofing. Uses a
  private context key (contextKey{}) instead of the header string.
- writeIamErrorResponse in both iamapi and embedded IAM now accepts
  reqID as a parameter instead of calling Ensure() internally, ensuring
  a single request ID per request lifecycle.
- The nil-iamError branch in writeIamErrorResponse now writes a 500
  Internal Server Error response instead of returning silently.
- Updated tests to set request IDs via context (not headers) and added
  tests for spoofing prevention and context reuse.

* sts: add request-id consistency assertions to ActionInBody tests

* test: update admin test to expect server-generated request IDs

The test previously sent a client x-amz-request-id header and expected
it echoed back. Since Ensure() now ignores client headers to prevent
spoofing, update the test to verify the server returns a non-empty
server-generated request ID instead.

* iam: add generic WithRequestID helper alongside reflection-based fallback

Add WithRequestID[T] that uses generics to take the address of a value
type, satisfying the pointer receiver on SetRequestId without reflection.

The existing SetResponseRequestID is kept for the two call sites that
operate on interface{} (from large action switches where the concrete
type varies at runtime). Generics cannot replace reflection there since
Go cannot infer type parameters from interface{}.

* Remove reflection and generics from request ID setting

Call SetRequestId directly on concrete response types in each switch
branch before boxing into interface{}, eliminating the need for
WithRequestID (generics) and SetResponseRequestID (reflection).

* iam: return pointer responses in action dispatch

* Fix IAM error handling consistency and ensure request IDs on all responses

- UpdateUser/CreatePolicy error branches: use writeIamErrorResponse instead
  of s3err.WriteErrorResponse to preserve IAM formatting and request ID
- ExecuteAction: accept reqID parameter and generate one if empty, ensuring
  every response carries a RequestId regardless of caller

* Clean up inline policies on DeleteUser and UpdateUser rename

DeleteUser: remove InlinePolicies[userName] from policy storage before
removing the identity, so policies are not orphaned.

UpdateUser: move InlinePolicies[userName] to InlinePolicies[newUserName]
when renaming, so GetUserPolicy/DeleteUserPolicy work under the new name.

Both operations persist the updated policies and return an error if
the storage write fails, preventing partial state.

weed/s3api/s3err/error_handler.go

@@ -3,15 +3,14 @@ package s3err
 import (
 	"bytes"
 	"encoding/xml"
-	"fmt"
 	"net/http"
 	"strconv"
 	"strings"
-	"time"
 
 	"github.com/aws/aws-sdk-go/private/protocol/xml/xmlutil"
 	"github.com/gorilla/mux"
 	"github.com/seaweedfs/seaweedfs/weed/glog"
+	"github.com/seaweedfs/seaweedfs/weed/util/request_id"
 )
 
 type mimeType string
@@ -41,6 +40,7 @@ func WriteEmptyResponse(w http.ResponseWriter, r *http.Request, statusCode int)
 }
 
 func WriteErrorResponse(w http.ResponseWriter, r *http.Request, errorCode ErrorCode) {
+	r, reqID := request_id.Ensure(r)
 	vars := mux.Vars(r)
 	bucket := vars["bucket"]
 	object := vars["object"]
@@ -49,19 +49,19 @@ func WriteErrorResponse(w http.ResponseWriter, r *http.Request, errorCode ErrorC
 	}
 
 	apiError := GetAPIError(errorCode)
-	errorResponse := getRESTErrorResponse(apiError, r.URL.Path, bucket, object)
+	errorResponse := getRESTErrorResponse(apiError, r.URL.Path, bucket, object, reqID)
 	WriteXMLResponse(w, r, apiError.HTTPStatusCode, errorResponse)
 	PostLog(r, apiError.HTTPStatusCode, errorCode)
 }
 
-func getRESTErrorResponse(err APIError, resource string, bucket, object string) RESTErrorResponse {
+func getRESTErrorResponse(err APIError, resource string, bucket, object, requestID string) RESTErrorResponse {
 	return RESTErrorResponse{
 		Code:       err.Code,
 		BucketName: bucket,
 		Key:        object,
 		Message:    err.Description,
 		Resource:   resource,
-		RequestID:  fmt.Sprintf("%d", time.Now().UnixNano()),
+		RequestID:  requestID,
 	}
 }
 
@@ -75,7 +75,8 @@ func EncodeXMLResponse(response interface{}) []byte {
 }
 
 func setCommonHeaders(w http.ResponseWriter, r *http.Request) {
-	w.Header().Set("x-amz-request-id", fmt.Sprintf("%d", time.Now().UnixNano()))
+	_, reqID := request_id.Ensure(r)
+	w.Header().Set(request_id.AmzRequestIDHeader, reqID)
 	w.Header().Set("Accept-Ranges", "bytes")
 
 	// Handle CORS headers for requests with Origin header