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/s3api_sts.go

@@ -19,6 +19,7 @@ import (
 	"github.com/seaweedfs/seaweedfs/weed/iam/sts"
 	"github.com/seaweedfs/seaweedfs/weed/iam/utils"
 	"github.com/seaweedfs/seaweedfs/weed/s3api/s3err"
+	"github.com/seaweedfs/seaweedfs/weed/util/request_id"
 )
 
 // STS API constants matching AWS STS specification
@@ -97,6 +98,7 @@ func (h *STSHandlers) getAccountID() string {
 // HandleSTSRequest is the main entry point for STS requests
 // It routes requests based on the Action parameter
 func (h *STSHandlers) HandleSTSRequest(w http.ResponseWriter, r *http.Request) {
+	r, _ = request_id.Ensure(r)
 	if err := r.ParseForm(); err != nil {
 		h.writeSTSErrorResponse(w, r, STSErrInvalidParameterValue, err)
 		return
@@ -224,7 +226,7 @@ func (h *STSHandlers) handleAssumeRoleWithWebIdentity(w http.ResponseWriter, r *
 			SubjectFromWebIdentityToken: response.AssumedRoleUser.Subject,
 		},
 	}
-	xmlResponse.ResponseMetadata.RequestId = fmt.Sprintf("%d", time.Now().UnixNano())
+	xmlResponse.ResponseMetadata.RequestId = request_id.GetFromRequest(r)
 
 	s3err.WriteXMLResponse(w, r, http.StatusOK, xmlResponse)
 }
@@ -354,7 +356,7 @@ func (h *STSHandlers) handleAssumeRole(w http.ResponseWriter, r *http.Request) {
 			AssumedRoleUser: assumedUser,
 		},
 	}
-	xmlResponse.ResponseMetadata.RequestId = fmt.Sprintf("%d", time.Now().UnixNano())
+	xmlResponse.ResponseMetadata.RequestId = request_id.GetFromRequest(r)
 
 	s3err.WriteXMLResponse(w, r, http.StatusOK, xmlResponse)
 }
@@ -495,7 +497,7 @@ func (h *STSHandlers) handleAssumeRoleWithLDAPIdentity(w http.ResponseWriter, r
 			AssumedRoleUser: assumedUser,
 		},
 	}
-	xmlResponse.ResponseMetadata.RequestId = fmt.Sprintf("%d", time.Now().UnixNano())
+	xmlResponse.ResponseMetadata.RequestId = request_id.GetFromRequest(r)
 
 	s3err.WriteXMLResponse(w, r, http.StatusOK, xmlResponse)
 }
@@ -731,7 +733,7 @@ func (h *STSHandlers) writeSTSErrorResponse(w http.ResponseWriter, r *http.Reque
 	}
 
 	response := STSErrorResponse{
-		RequestId: fmt.Sprintf("%d", time.Now().UnixNano()),
+		RequestId: request_id.GetFromRequest(r),
 	}
 
 	// Server-side errors use "Receiver" type per AWS spec