Add credential storage (#6938)

* add credential store interface

* load credential.toml

* lint

* create credentialManager with explicit store type

* add type name

* InitializeCredentialManager

* remove unused functions

* fix missing import

* fix import

* fix nil configuration

weed/command/iam.go

@@ -3,9 +3,10 @@ package command
 import (
 	"context"
 	"fmt"
-	"github.com/seaweedfs/seaweedfs/weed/util/version"
 	"net/http"
 
+	"github.com/seaweedfs/seaweedfs/weed/util/version"
+
 	"time"
 
 	"github.com/gorilla/mux"
@@ -15,6 +16,12 @@ import (
 	"github.com/seaweedfs/seaweedfs/weed/pb/filer_pb"
 	"github.com/seaweedfs/seaweedfs/weed/security"
 	"github.com/seaweedfs/seaweedfs/weed/util"
+
+	// Import credential stores to register them
+	_ "github.com/seaweedfs/seaweedfs/weed/credential/filer_etc"
+	_ "github.com/seaweedfs/seaweedfs/weed/credential/memory"
+	_ "github.com/seaweedfs/seaweedfs/weed/credential/postgres"
+	_ "github.com/seaweedfs/seaweedfs/weed/credential/sqlite"
 )
 
 var (