Refactor Admin UI to use unified IAM storage and add MultipleFileStore (#8101)

* Refactor Admin UI to use unified IAM storage and add MultipleFileStore

* Address PR feedback: fix renames, error handling, and sync logic in FilerMultipleStore

* Address refined PR feedback: safe rename order, rollback logic, and structural sync refinement

* Optimize LoadConfiguration: use streaming callback for memory efficiency

* Refactor UpdateUser: log rollback failures during rename

* Implement PolicyManager for FilerMultipleStore

* include the filer_multiple backend configuration

* Implement cross-S3 synchronization and proper shutdown for all IAM backends

* Extract Admin UI refactoring to a separate PR

weed/command/imports.go

@@ -34,4 +34,7 @@ import (
 	_ "github.com/seaweedfs/seaweedfs/weed/filer/tarantool"
 	_ "github.com/seaweedfs/seaweedfs/weed/filer/tikv"
 	_ "github.com/seaweedfs/seaweedfs/weed/filer/ydb"
+
+	_ "github.com/seaweedfs/seaweedfs/weed/credential/filer_etc"
+	_ "github.com/seaweedfs/seaweedfs/weed/credential/filer_multiple"
 )

weed/command/s3.go

@@ -297,6 +297,7 @@ func (s3opt *S3Options) startS3Server() bool {
 	if s3ApiServer_err != nil {
 		glog.Fatalf("S3 API Server startup error: %v", s3ApiServer_err)
 	}
+	defer s3ApiServer.Shutdown()
 
 	if *s3opt.portGrpc == 0 {
 		*s3opt.portGrpc = 10000 + *s3opt.port

weed/command/scaffold/credential.toml

@@ -12,6 +12,11 @@
 enabled = true
 # filer address and grpc_dial_option will be automatically configured by the server
 
+# Multi-file credential store (stores each user/policy in a separate file)
+[credential.filer_multiple]
+enabled = false
+# filer address and grpc_dial_option will be automatically configured by the server
+
 
 # PostgreSQL credential store (recommended for multi-node deployments)
 [credential.postgres]