Simple S3 client (#836)

This functionality is intended to be used to manage datasets for test cases, but may be useful elsewhere in the future.

- **Add S3 client with AWS Signature V4 (SigV4) signing** — new `S3Client` in `zenutil/cloud/` supporting `GetObject`, `PutObject`, `DeleteObject`, `HeadObject`, and `ListObjects` operations
- **Add EC2 IMDS credential provider** — automatically fetches and refreshes temporary AWS credentials from the EC2 Instance Metadata Service (IMDSv2) for use by the S3 client
- **Add SigV4 signing library** — standalone implementation of AWS Signature Version 4 request signing (headers and query-string presigning)
- **Add path-style addressing support** — enables compatibility with S3-compatible stores like MinIO (in addition to virtual-hosted style)
- **Add S3 integration tests** — includes a `MinioProcess` test helper that spins up a local MinIO server, plus integration tests exercising the S3 client end-to-end
- **Add S3-backed `HttpObjectStoreService` tests** — integration tests verifying the zenserver object store works against an S3 backend
- **Refactor mock IMDS into `zenutil/cloud/`** — moved and generalized the mock IMDS server from `zencompute` so it can be reused by both compute and S3 credential tests

1 files changed, 23 insertions, 0 deletions

diff --git a/src/zenutil/cloud/cloudprovider.cpp b/src/zenutil/cloud/cloudprovider.cpp
new file mode 100644
index 000000000..e32a50c64
--- /dev/null
+++ b/src/zenutil/cloud/cloudprovider.cpp
@@ -0,0 +1,23 @@
+// Copyright Epic Games, Inc. All Rights Reserved.
+
+#include <zenutil/cloud/cloudprovider.h>
+
+namespace zen::compute {
+
+std::string_view
+ToString(CloudProvider Provider)
+{
+	switch (Provider)
+	{
+		case CloudProvider::AWS:
+			return "AWS";
+		case CloudProvider::Azure:
+			return "Azure";
+		case CloudProvider::GCP:
+			return "GCP";
+		default:
+			return "None";
+	}
+}
+
+}  // namespace zen::compute