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

weed/s3api/auth_credentials_test.go

@@ -13,6 +13,9 @@ import (
 
 	"github.com/seaweedfs/seaweedfs/weed/pb/iam_pb"
 	jsonpb "google.golang.org/protobuf/encoding/protojson"
+
+	_ "github.com/seaweedfs/seaweedfs/weed/credential/filer_etc"
+	_ "github.com/seaweedfs/seaweedfs/weed/credential/memory"
 )
 
 func TestIdentityListFileFormat(t *testing.T) {
@@ -742,3 +745,48 @@ func TestSignatureVerificationDoesNotCheckPermissions(t *testing.T) {
 	t.Log("Signature verification no longer checks for Write permission")
 	t.Log("This allows list-only and read-only users to authenticate via AWS Signature V4")
 }
+
+func TestStaticIdentityProtection(t *testing.T) {
+	iam := NewIdentityAccessManagement(&S3ApiServerOption{})
+
+	// Add a static identity
+	staticIdent := &Identity{
+		Name:     "static-user",
+		IsStatic: true,
+	}
+	iam.m.Lock()
+	if iam.nameToIdentity == nil {
+		iam.nameToIdentity = make(map[string]*Identity)
+	}
+	iam.identities = append(iam.identities, staticIdent)
+	iam.nameToIdentity[staticIdent.Name] = staticIdent
+	iam.m.Unlock()
+
+	// Add a dynamic identity
+	dynamicIdent := &Identity{
+		Name:     "dynamic-user",
+		IsStatic: false,
+	}
+	iam.m.Lock()
+	iam.identities = append(iam.identities, dynamicIdent)
+	iam.nameToIdentity[dynamicIdent.Name] = dynamicIdent
+	iam.m.Unlock()
+
+	// Try to remove static identity
+	iam.RemoveIdentity("static-user")
+
+	// Verify static identity still exists
+	iam.m.RLock()
+	_, ok := iam.nameToIdentity["static-user"]
+	iam.m.RUnlock()
+	assert.True(t, ok, "Static identity should not be removed")
+
+	// Try to remove dynamic identity
+	iam.RemoveIdentity("dynamic-user")
+
+	// Verify dynamic identity is removed
+	iam.m.RLock()
+	_, ok = iam.nameToIdentity["dynamic-user"]
+	iam.m.RUnlock()
+	assert.False(t, ok, "Dynamic identity should have been removed")
+}