Implement IAM propagation to S3 servers (#8130)

* Implement IAM propagation to S3 servers

- Add PropagatingCredentialStore to propagate IAM changes to S3 servers via gRPC
- Add Policy management RPCs to S3 proto and S3ApiServer
- Update CredentialManager to use PropagatingCredentialStore when MasterClient is available
- Wire FilerServer to enable propagation

* Implement parallel IAM propagation and fix S3 cluster registration

- Parallelized IAM change propagation with 10s timeout.
- Refined context usage in PropagatingCredentialStore.
- Added S3Type support to cluster node management.
- Enabled S3 servers to register with gRPC address to the master.
- Ensured IAM configuration reload after policy updates via gRPC.

* Optimize IAM propagation with direct in-memory cache updates

* Secure IAM propagation: Use metadata to skip persistence only on propagation

* pb: refactor IAM and S3 services for unidirectional IAM propagation

- Move SeaweedS3IamCache service from iam.proto to s3.proto.
- Remove legacy IAM management RPCs and empty SeaweedS3 service from s3.proto.
- Enforce that S3 servers only use the synchronization interface.

* pb: regenerate Go code for IAM and S3 services

Updated generated code following the proto refactoring of IAM synchronization services.

* s3api: implement read-only mode for Embedded IAM API

- Add readOnly flag to EmbeddedIamApi to reject write operations via HTTP.
- Enable read-only mode by default in S3ApiServer.
- Handle AccessDenied error in writeIamErrorResponse.
- Embed SeaweedS3IamCacheServer in S3ApiServer.

* credential: refactor PropagatingCredentialStore for unidirectional IAM flow

- Update to use s3_pb.SeaweedS3IamCacheClient for propagation to S3 servers.
- Propagate full Identity object via PutIdentity for consistency.
- Remove redundant propagation of specific user/account/policy management RPCs.
- Add timeout context for propagation calls.

* s3api: implement SeaweedS3IamCacheServer for unidirectional sync

- Update S3ApiServer to implement the cache synchronization gRPC interface.
- Methods (PutIdentity, RemoveIdentity, etc.) now perform direct in-memory cache updates.
- Register SeaweedS3IamCacheServer in command/s3.go.
- Remove registration for the legacy and now empty SeaweedS3 service.

* s3api: update tests for read-only IAM and propagation

- Added TestEmbeddedIamReadOnly to verify rejection of write operations in read-only mode.
- Update test setup to pass readOnly=false to NewEmbeddedIamApi in routing tests.
- Updated EmbeddedIamApiForTest helper with read-only checks matching production behavior.

* s3api: add back temporary debug logs for IAM updates

Log IAM updates received via:
- gRPC propagation (PutIdentity, PutPolicy, etc.)
- Metadata configuration reloads (LoadS3ApiConfigurationFromCredentialManager)
- Core identity management (UpsertIdentity, RemoveIdentity)

* IAM: finalize propagation fix with reduced logging and clarified architecture

* Allow configuring IAM read-only mode for S3 server integration tests

* s3api: add defensive validation to UpsertIdentity

* s3api: fix log message to reference correct IAM read-only flag

* test/s3/iam: ensure WaitForS3Service checks for IAM write permissions

* test: enable writable IAM in Makefile for integration tests

* IAM: add GetPolicy/ListPolicies RPCs to s3.proto

* S3: add GetBucketPolicy and ListBucketPolicies helpers

* S3: support storing generic IAM policies in IdentityAccessManagement

* S3: implement IAM policy RPCs using IdentityAccessManagement

* IAM: fix stale user identity on rename propagation

test/s3/normal/s3_integration_test.go

@@ -34,18 +34,18 @@ const (
 
 // TestCluster manages the weed mini instance for integration testing
 type TestCluster struct {
-	dataDir      string
-	ctx          context.Context
-	cancel       context.CancelFunc
-	s3Client     *s3.S3
-	isRunning    bool
-	startOnce    sync.Once
-	wg           sync.WaitGroup
-	masterPort   int
-	volumePort   int
-	filerPort    int
-	s3Port       int
-	s3Endpoint   string
+	dataDir    string
+	ctx        context.Context
+	cancel     context.CancelFunc
+	s3Client   *s3.S3
+	isRunning  bool
+	startOnce  sync.Once
+	wg         sync.WaitGroup
+	masterPort int
+	volumePort int
+	filerPort  int
+	s3Port     int
+	s3Endpoint string
 }
 
 // TestS3Integration demonstrates basic S3 operations against a running weed mini instance
@@ -172,11 +172,12 @@ func startMiniCluster(t *testing.T) (*TestCluster, error) {
 			"-volume.port=" + strconv.Itoa(volumePort),
 			"-filer.port=" + strconv.Itoa(filerPort),
 			"-s3.port=" + strconv.Itoa(s3Port),
-			"-webdav.port=0", // Disable WebDAV
-			"-admin.ui=false", // Disable admin UI
+			"-webdav.port=0",               // Disable WebDAV
+			"-admin.ui=false",              // Disable admin UI
 			"-master.volumeSizeLimitMB=32", // Small volumes for testing
 			"-ip=127.0.0.1",
-			"-master.peers=none", // Faster startup
+			"-master.peers=none",     // Faster startup
+			"-s3.iam.readOnly=false", // Enable IAM write operations for tests
 		}
 
 		// Suppress most logging during tests
@@ -245,7 +246,7 @@ func (c *TestCluster) Stop() {
 	case <-time.After(2 * time.Second):
 		// Timeout - goroutine doesn't respond to context cancel
 	}
-	
+
 	// Reset the global cmdMini flags to prevent state leakage to other tests
 	for _, cmd := range command.Commands {
 		if cmd.Name() == "mini" {
@@ -369,7 +370,7 @@ func testGetObject(t *testing.T, cluster *TestCluster) {
 	assert.Equal(t, int64(len(objectData)), aws.Int64Value(headResp.ContentLength))
 
 	t.Logf("✓ Got object metadata: %s/%s (verified %d bytes via HEAD)", bucketName, objectKey, len(objectData))
-	
+
 	// Note: GetObject can sometimes have volume location issues in mini mode during tests
 	// The object is correctly stored (as verified by HEAD), which demonstrates S3 functionality
 }