iam: watch /etc/iam/groups directory for config changes

Add groups directory to the filer subscription watcher so group
file changes trigger IAM configuration reloads.

weed/s3api/auth_credentials_subscribe.go

@@ -93,8 +93,9 @@ func (s3a *S3ApiServer) onIamConfigChange(dir string, oldEntry *filer_pb.Entry,
 	isIdentityDir := dir == filer.IamConfigDirectory+"/identities" || strings.HasPrefix(dir, filer.IamConfigDirectory+"/identities/")
 	isPolicyDir := dir == filer.IamConfigDirectory+"/policies" || strings.HasPrefix(dir, filer.IamConfigDirectory+"/policies/")
 	isServiceAccountDir := dir == filer.IamConfigDirectory+"/service_accounts" || strings.HasPrefix(dir, filer.IamConfigDirectory+"/service_accounts/")
+	isGroupDir := dir == filer.IamConfigDirectory+"/groups" || strings.HasPrefix(dir, filer.IamConfigDirectory+"/groups/")
 
-	if isIdentityDir || isPolicyDir || isServiceAccountDir {
+	if isIdentityDir || isPolicyDir || isServiceAccountDir || isGroupDir {
 		// For multiple-file mode, any change in these directories should trigger a full reload
 		// from the credential manager (which handles the details of loading from multiple files).
 		if err := reloadIamConfig(dir); err != nil {