管理者はモデレーターに変更できないように (#5970)

* 管理者をモデレーターに変更できないように

* Change error message

src/client/components/user-moderate-dialog.vue

@@ -3,7 +3,7 @@
 	<template #header><mk-user-name :user="user"/></template>
 	<div class="vrcsvlkm">
 		<mk-button @click="resetPassword()" primary>{{ $t('resetPassword') }}</mk-button>
-		<mk-switch v-if="$store.state.i.isAdmin" @change="toggleModerator()" v-model="moderator">{{ $t('moderator') }}</mk-switch>
+		<mk-switch v-if="$store.state.i.isAdmin && !user.isAdmin" @change="toggleModerator()" v-model="moderator">{{ $t('moderator') }}</mk-switch>
 		<mk-switch @change="toggleSilence()" v-model="silenced">{{ $t('silence') }}</mk-switch>
 		<mk-switch @change="toggleSuspend()" v-model="suspended">{{ $t('suspend') }}</mk-switch>
 	</div>

src/server/api/endpoints/admin/moderators/add.ts

@@ -32,6 +32,10 @@ export default define(meta, async (ps) => {
 		throw new Error('user not found');
 	}
 
+	if (user.isAdmin) {
+		throw new Error('cannot mark as moderator if admin user');
+	}
+
 	await Users.update(user.id, {
 		isModerator: true
 	});