[exporter/awss3] Fix outdated StorageClass and ACL validation by using AWS SDK types

[57Ajay]

fixes #46825

Problem

The awss3exporter config validation in config.go uses hardcoded maps to validate StorageClass and ACL values. The StorageClass allowlist was missing several valid AWS S3 storage classes:

Storage Class	Status
GLACIER_IR	Missing -- rejected as invalid
REDUCED_REDUNDANCY	Missing -- rejected as invalid
EXPRESS_ONEZONE	Missing -- rejected as invalid

This caused users configuring any of these storage classes to receive the error:

Error: invalid configuration: exporters::awss3: invalid StorageClass

The same maintenance concern applies to the ACL validation map - while it happens to be complete today, it is equally susceptible to going stale if AWS introduces new canned ACL values in the future.

Root Cause

The exporter treats StorageClass and ACL as pass-through values - the config string is cast directly to the corresponding AWS SDK type (s3types.StorageClass / s3types.ObjectCannedACL) and forwarded to the S3 API with no class-specific or ACL-specific logic. The hardcoded validation maps were therefore both redundant and incomplete.

Fix

Replaced both hardcoded validation maps with dynamic lookups using the AWS SDK's own type values:

• StorageClass: now validated against s3types.StorageClassStandard.Values()
• ACL: now validated against s3types.ObjectCannedACLPrivate.Values()

This ensures validation stays in sync with the AWS SDK automatically, eliminating the need for manual updates when AWS introduces new storage classes or ACL types.

Testing

• Added test cases to TestConfig_Validate for GLACIER_IR, REDUCED_REDUNDANCY, and EXPRESS_ONEZONE storage classes -- these fail against the old code and pass with the fix.
• Added a negative test case for a truly invalid storage class (FAKE_CLASS) to verify rejection still works correctly.

Changes

File	Change
exporter/awss3exporter/config.go	Replaced hardcoded validStorageClasses and validACLs maps with AWS SDK .Values() lookups
exporter/awss3exporter/config_test.go	Added test cases for missing storage classes and invalid class rejection
.chloggen/fix-awss3exporter-storage-class-acl-validation.yaml	Changelog entry

[57Ajay]

/rerun

[paulojmdias]

LGTM