fix: use main user for s3tests tenant to prevent teardown failures (#1597)

.github/s3tests/s3tests.conf

@@ -120,7 +120,11 @@ secret_key = ${S3_ALT_SECRET_KEY}
 display_name = RustFS Tenant Tester
 
 # tenant user_id
-user_id = rustfstenant
+# Note: Using same user_id as main to avoid teardown failures.
+# RustFS does not currently support multi-tenancy, so the tenant client
+# effectively operates as the main user. This ensures nuke_prefixed_buckets()
+# in s3-tests teardown can successfully clean up resources.
+user_id = rustfsadmin
 
 # tenant AWS access key
 access_key = ${S3_ACCESS_KEY}
@@ -132,7 +136,11 @@ secret_key = ${S3_SECRET_KEY}
 email = tenant@rustfs.local
 
 # tenant name
-tenant = testx
+# Note: Empty tenant name to avoid multi-tenant path issues during teardown.
+# When s3-tests calls get_tenant_client(), it uses this tenant value in requests.
+# An empty value makes the tenant client behave like the main client, preventing
+# "bucket not found" errors when teardown tries to clean up test buckets.
+tenant =
 
 #following section needs to be added for all sts-tests
 [iam]