* fix: IAM authentication with AWS Signature V4 and environment credentials
Three key fixes for authenticated IAM requests to work:
1. Fix request body consumption before signature verification
- iamMatcher was calling r.ParseForm() which consumed POST body
- This broke AWS Signature V4 verification on subsequent reads
- Now only check query string in matcher, preserving body for verification
- File: weed/s3api/s3api_server.go
2. Preserve environment variable credentials across config reloads
- After IAM mutations, config reload overwrote env var credentials
- Extract env var loading into loadEnvironmentVariableCredentials()
- Call after every config reload to persist credentials
- File: weed/s3api/auth_credentials.go
3. Add authenticated IAM tests and test infrastructure
- New TestIAMAuthenticated suite with AWS SDK + Signature V4
- Dynamic port allocation for independent test execution
- Flag reset to prevent state leakage between tests
- CI workflow to run S3 and IAM tests separately
- Files: test/s3/example/*, .github/workflows/s3-example-integration-tests.yml
All tests pass:
- TestIAMCreateUser (unauthenticated)
- TestIAMAuthenticated (with AWS Signature V4)
- S3 integration tests
* fmt
* chore: rename test/s3/example to test/s3/normal
* simplify: CI runs all integration tests in single job
* Update s3-example-integration-tests.yml
* ci: run each test group separately to avoid raft registry conflicts
