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, 11 insertions, 0 deletions

diff --git a/src/zenserver/xmake.lua b/src/zenserver/xmake.lua
index b619c5548..7bfc3575e 100644
--- a/src/zenserver/xmake.lua
+++ b/src/zenserver/xmake.lua
@@ -36,6 +36,7 @@ target("zenserver")
     add_packages("json11")
     add_packages("lua")
     add_packages("consul")
+    add_packages("minio")
     add_packages("oidctoken")
     add_packages("nomad")
 
@@ -215,6 +216,16 @@ target("zenserver")
             copy_if_newer(path.join(installdir, "bin", consul_bin), path.join(target:targetdir(), consul_bin), consul_bin)
         end
 
+        local minio_pkg = target:pkg("minio")
+        if minio_pkg then
+            local installdir = minio_pkg:installdir()
+            local minio_bin = "minio"
+            if is_plat("windows") then
+                minio_bin = "minio.exe"
+            end
+            copy_if_newer(path.join(installdir, "bin", minio_bin), path.join(target:targetdir(), minio_bin), minio_bin)
+        end
+
         local oidctoken_pkg = target:pkg("oidctoken")
         if oidctoken_pkg then
             local installdir = oidctoken_pkg:installdir()