feat(#707): secure Discord service ingress

apps/gateway/src/plugin/plugin.module.ts

@@ -50,19 +50,41 @@ class TelegramChannelPluginAdapter implements IChannelPlugin {
 
 const DEFAULT_GATEWAY_URL = 'http://localhost:14242';
 
+function requiredDiscordAllowlist(name: string): string[] {
+  const value = process.env[name]
+    ?.split(',')
+    .map((id: string): string => id.trim())
+    .filter((id: string): boolean => id.length > 0);
+  if (!value || value.length === 0) {
+    throw new Error(`${name} is required when DISCORD_BOT_TOKEN is configured`);
+  }
+  return value;
+}
+
 function createPluginRegistry(): IChannelPlugin[] {
   const plugins: IChannelPlugin[] = [];
   const discordToken = process.env['DISCORD_BOT_TOKEN'];
   const discordGuildId = process.env['DISCORD_GUILD_ID'];
   const discordGatewayUrl = process.env['DISCORD_GATEWAY_URL'] ?? DEFAULT_GATEWAY_URL;
+  const discordServiceToken = process.env['DISCORD_SERVICE_TOKEN'];
+  const discordServiceUserId = process.env['DISCORD_SERVICE_USER_ID'];
 
   if (discordToken) {
+    if (!discordServiceToken || !discordServiceUserId) {
+      throw new Error(
+        'DISCORD_SERVICE_TOKEN and DISCORD_SERVICE_USER_ID are required when DISCORD_BOT_TOKEN is configured',
+      );
+    }
     plugins.push(
       new DiscordChannelPluginAdapter(
         new DiscordPlugin({
           token: discordToken,
           guildId: discordGuildId,
           gatewayUrl: discordGatewayUrl,
+          serviceToken: discordServiceToken,
+          allowedGuildIds: requiredDiscordAllowlist('DISCORD_ALLOWED_GUILD_IDS'),
+          allowedChannelIds: requiredDiscordAllowlist('DISCORD_ALLOWED_CHANNEL_IDS'),
+          allowedUserIds: requiredDiscordAllowlist('DISCORD_ALLOWED_USER_IDS'),
         }),
       ),
     );