Fix Prosody room topic:

Due to a bug in mod_muc_http_defaults (https://hg.prosody.im/prosody-modules/rev/6d99ddd99694),
room topics were badly configured. The plugin will fix them at startup, and stops trying to set the subject.

server/lib/prosody/ctl.ts

@@ -5,6 +5,7 @@ import {
   ensureProsodyCertificates, startProsodyCertificatesRenewCheck, stopProsodyCertificatesRenewCheck
 } from './certificates'
 import { disableProxyRoute, enableProxyRoute } from '../routers/webchat'
+import { fixRoomSubject } from './fix-room-subject'
 import * as fs from 'fs'
 import * as child_process from 'child_process'
 
@@ -71,6 +72,12 @@ async function prepareProsody (options: RegisterServerOptions): Promise<void> {
     filePaths.appImageExtractPath
   )
 
+  try {
+    await fixRoomSubject(options, filePaths)
+  } catch (err) {
+    logger.error(err)
+  }
+
   const appImageToExtract = filePaths.appImageToExtract
   if (!appImageToExtract) {
     return